Re: 87 4.3 vs. 88 4.3
Don't know for sure but this may be the reason. 87 was the first year for a 4.3 in the S-truck. It seems reasonable that they made a whole whack of changes for 88 to correct problems, and that after 88, once they figured it all otu, things stayed fairly similar ( thus the blanket installation of 88 and up.) Don't know the specifics of the Astro. Talk to a dealer or a mechanic, or phone the carn manufacturer. Thew will tell you.