A recent thread on another forum showed the old L98 upper portions changed/evolved over the years. The person found out through allot of troubleshooting the IAC passages from the throttle body to within the manifold were different.
I am wondering if there are any internal differences within the LT1 manifolds.
I know some people have put different years on, like myself after doing modifications.

 

Ttt

 

a few things that are differrent maybe some more around, but the 1993 intake did not have the slanted peice out of the top of the intake where the fuel rails set on 94+,
also the only other main difference that i can think about, is that the 95 or maybe 96+ intakes run the PCV From the front of the intake where the 93 and 94 models run it on the side right next to the valve itself.

 

There are 4-5 different castings, the most signifigant difference was mentioned above, the fuel rail crossover. If you are running Stock Eliminator then this subject might be worthwhile, if not then only thing you are going to gain is satisfied curiosity.

Put it this way, my car wear the intake off a 96 4.3l V8, was street ported by AI and doesn't seem to be hurting anything.

 

The PCV vacuum connection is irrelevant.... the tapped connections are the same on all the manifolds. They just put a small plug in the hole under the throttle body on the 93/94 engines.

 

Not argueing by any means injuneer but the 1993 intakes definatly do not have a plug under the throttle body for a provision of the pcv as you say

1994's may have it