hey, looky what I found...
Actually, I knew it was there for ten years now....
Heres the link, and a copy of the goods from that link...
http://www.astrosafari.com/old/ib/ AstroZam, Justice, I'm sure y'all remember that place eh?
If you click on the tech info tab, you find rear axle info as well as some stuff about how to do a gen 1 to Gen 2 nose swap, dutch doors from barn doors etc. Its all good stuff.
Note: I would be shot for doing just this at "that other site".....
The RPO CODE on the sticker only shows which rear axle was installed at the factory. If you are not the original owner of your van you don't know for sure if the axle has been replaced or not. ONE way to be almost SURE what your rear axle ratio is will be to look at the actual factory code stamped on the axle itself. But the only certain way is to loo at the numbers stamped on the crown and pinion gears...
AXLE TUBE CODES: The surefire way to find out which gear ratio your rear axle has is to look at the spot you see pointed out in the image above. The parking brake cable runs right across the area you need to see. You will need to clean off the axle tube well to see the letters-numbers clearly. You will notice the code is located on the front of the tube on the passengers side of the van. However, I have found that on 1988 and older, the code is found on the front of the drivers side axle tube. NOTE! The first 3 letters of the code stamp are the ones that matter. Just compare them to the list provided below to determine you gear ratio.
FAA: 7.5", 2.56 open (1985-1986 Astro)
FAF: 7.5", 2.73 open (1988 Astro)
FAG: 7.5", 3.08 open (1988-1989 Astro)
FAH: 7.5", 3.42 open (1988-1989 Astro)
FAJ: 7.5", 2.73 posi (1988 Astro)
FAK: 7.5", 3.08 posi (1988-1989 Astro)
FAL: 7.5", 3.42 posi (1988-1989 Astro)
FAM: 7.5", 3.73 open (1988-1989 Astro)
FAN: 7.5", 3.73 posi (1988-1989 Astro)
FAP: 7.5", 4.10 open (1988-1989 Astro)
FAR: 7.5", 4.10 posi (1988-1989 Astro)
FAS: 7.5", 3.23 open (1988-1989 Astro)
FAT: 7.5", 3.23 posi (1988-1989 Astro)
FBA: 7.5", 2.56 posi (1985-1986 Astro)
FCA: 7.5", 2.73 open (1985-1987 Astro)
FCB: 7.5", 2.73 posi (1985-1986 Astro)
FFA: 7.5", 3.08 open (1985-1987 Astro)
FFB: 7.5", 3.08 posi (1985-1986 Astro)
FMA: 7.5", 3.42 open (1985-1987 Astro)
FMB: 7.5", 3.42 posi (1985-1986 Astro)
FRA: 7.5", 3.73 open (1985-1987 Astro)
FRB: 7.5", 3.73 posi (1985-1986 Astro)
FSA: 7.5", 4.11 open (1985-1986 Astro)
FSD: 7.5", 4.11 posi (1985-1986 Astro)
GWH: 7.5", 4.10 open (1985-1987 Astro)
GWJ: 7.5", 4.10 posi (1985-1986 Astro)
HZA: 7.5", 2.73 posi (1987 Astro)
HZB: 7.5", 3.08 posi (1987 Astro)
HZC: 7.5", 3.42 posi (1987 Astro)
HZF: 7.5", 3.73 posi (1986 Astro)
HZG: 7.5", 4.11 posi (1986-1987 Astro)
KJM: 7.5", 2.73 open (1987 Astro)
KJN: 7.5", 3.08 open (1987 Astro)
KJP: 7.5", 3.42 open (1987 Astro)
KJR: 7.5", 2.73 posi (1987 Astro)
KJS: 7.5", 3.08 posi (1987 Astro)
KJT: 7.5", 3.42 posi (1987 Astro)
KJU: 7.5", 3.73 open (1987 Astro)
KJW: 7.5", 3.73 posi (1987 Astro)
KJX: 7.5", 4.10 open (1987 Astro)
KJY: 7.5", 4.10 posi (1987 Astro)
KRK: 7.5", 2.73 open (1987 Astro)
KRL: 7.5", 3.08 open (1987 Astro)
KRM: 7.5", 3.42 open (1987 Astro)
KRN: 7.5", 2.73 posi (1987 Astro)
KRP: 7.5", 3.08 posi (1987 Astro)
KRR: 7.5", 3.42 posi (1987 Astro)
KRS: 7.5", 3.73 open (1987 Astro)
KRT: 7.5", 3.73 posi (1987 Astro)
KRU: 7.5", 4.10 open (1987 Astro)
KRW: 7.5", 4.10 posi (1987 Astro)
PZK: 7.625", 4.10 open (1990 Astro)
PZL: 7.625", 4.10 posi (1990 Astro)
RHB: 7.625", 3.23 open (1990 Astro)
RHC: 7.625", 3.23 posi (1990 Astro)
RHD: 7.625", 3.42 open (1990 Astro)
RHF: 7.625", 3.42 posi (1990 Astro)
RHG: 7.625", 3.73 open (1990 Astro)
RHH: 7.625", 3.73 posi (1990 Astro)
RHL: 7.625", 3.23 open (1990 Astro)
RHM: 7.625", 3.42 open (1990 Astro)
RHN: 7.625", 3.73 open (1990 Astro)
RHP: 7.625", 3.23 posi (1990 Astro)
RHR: 7.625", 3.42 posi (1990 Astro)
RHS: 7.625", 3.73 posi (1990 Astro)
RHT: 7.625", 4.10 open (1990 Astro)
RHU: 7.625", 4.10 posi (1990 Astro)
SGF: 7.625", 3.23 open (1991 Astro)
SGG: 7.625", 3.23 posi (1991 Astro)
SGH: 7.625", 3.42 open (1991 Astro)
SGJ: 7.625", 3.42 posi (1991 Astro)
SGK: 7.625", 3.73 open (1991 Astro)
SGL: 7.625", 3.73 posi (1991 Astro)
SGM: 7.625", 4.10 open (1991 Astro)
SGN: 7.625", 4.10 posi (1991 Astro)
SGS: 7.625", 3.23 open (1991 Astro)
SGT: 7.625", 3.23 posi (1991 Astro)
SGU: 7.625", 3.42 open (1991 Astro)
SGW: 7.625", 3.42 posi (1991 Astro)
SGX: 7.625", 3.73 open (1991 Astro)
SGY: 7.625", 3.73 posi (1991 Astro)
SHD: 7.625", 3.23 open (1990 Astro)
SHF: 7.625", 3.23 posi (1990 Astro)
SHG: 7.625", 3.42 open (1990 Astro)
SHH: 7.625", 3.42 posi (1990 Astro)
SHJ: 7.625", 3.73 open (1990 Astro)
SHK: 7.625", 3.73 posi (1990 Astro)
SHL: 7.625", 4.10 open (1990 Astro)
SHM: 7.625", 4.10 posi (1990 Astro)
SHR: 7.625", 3.23 open (1990 Astro)
SHS: 7.625", 3.23 posi (1990 Astro)
SHT: 7.625", 3.42 open (1990 Astro)
SHU: 7.625", 3.42 posi (1990 Astro)
SHW: 7.625", 3.73 open (1990 Astro)
SHX: 7.625", 3.73 posi (1990 Astro)
SHY: 7.625", 4.10 open (1990 Astro)
SHZ: 7.625", 4.10 posi (1990 Astro)
TZD: 7.625", 3.23 open (late 1995 Astro)
TZF: 7.625", 3.23 posi (late 1995 Astro)
TZG: 7.625", 3.42 open (early 1995 Astro)
TZH: 7.625", 3.42 posi (late 1995 Astro)
TZJ: 7.625", 3.73 open (late 1995 Astro)
TZK: 7.625", 3.73 posi (late 1995 Astro)
USN: 7.625", 3.23 posi (1993-early 1995 Astro)
UTM: 7.625", 3.23 posi (1991-1992 Astro)
UTN: 7.625", 3.42 posi (1993-early 1995 Astro)
UTP: 7.625", 3.42 posi (1991 Astro)
UTR: 7.625", 3.73 open ('91-early '95 Astro)
UTS: 7.625", 3.73 posi ('91-early '95 Astro)
UTT: 7.625", 3.23 open (1991-1992 Astro)
UTU: 7.625", 3.23 posi (1991-1992 Astro)
UTW: 7.625", 3.42 open (1991-1992 Astro)
UTX: 7.625", 3.42 posi (1991-1992 Astro)
UTY: 7.625", open (1991-1992 Astro)
UTZ: 7.625", 3.73 posi (1991-1992 Astro)
VAC: 7.625", 3.23 open (1996-1997 Astro)
VBC: 7.625", 3.23 posi (1996-1997 Astro)
VCC: 7.625", 3.42 open (1996-1997 Astro)
VDC: 7.625", 3.42 posi (1996-1997 Astro)
VFC: 7.625", 3.73 open (1996-1997 Astro)
VGC: 7.625", 3.73 posi (1996-1997 Astro)
VKA: 7.625", 3.42 posi (1995 Astro-Export)
VKC: 7.625", 3.42 posi (1996-1997 Astro-Export)
VLA: 7.625", 3.73 posi (1995 Astro-Export)
VLC: 7.625", 3.73 posi (1996-1997 Astro-Export)