Well, my bottom end of my blazer needs to be rebuilt because there was a ton of gas that leaked into the engine.

I found a wrecked 99 astro van with a 4.3 in it for VERY cheap, can I swap the block into the blazer and just transfer over the intake/parts, or will it not work.

 

You can use the short block. There will be differences in the front cover and some other misc machining that has nothing to do with your '94, but the heads and accessories will swap over.

 

So it would be a direct swap?

 

This article should give you detailed information as to the changes that were made to the block.

Rebuilding the Chevy 262 by Doug Anderson courtesy of EngineBuilderMag.com

 

It didn't give a lot of info on 99 shortblocks, Would I have to do any maching or anything special for it to work?

 

In '98, the stanchions for the supports to the transmission were removed from the sides of the block as the oil pan was changed to an aluminum pan and the transmission bell housing was made to be removable and a full round bell housing. In that regard, you will no longer have any place for the supports to bolt to on the sides of the block. The oil pan will be an all aluminum pan, although you should be able to swap your old pan onto the new block.