I will be honest. I was never thought how to fix cars, So when you talk about an engine to me its like speaking another language, I don't know what you just said. But I just bought an 89 IROC-Z and I am looking for an engine to have my mechanic put it in for me. Now does it make a difference whether or not i buy a 2 bolt main or a 4 bolt main engine.

 

Get the 4 bolt 350 block if want over 450 hp, reving past 7 grand, nos, turbo, ect....Or if you have the extra money so you can say you have one. 2 bolt blocks are fine for any thing else, I have them in my car and use many stock GM parts which will support 450 hp for a long time. My 4 bolt block is for racing only with 630 hp.

 

For most street cars, a 2 bolt block should be fine. If it's going to wind up costing about the same, I'd go for the 4 bolt block. There are other differences in the blocks too though, such as roller vs non-roller lifters and fuel pump hole. Late model blocks that came in fuel injected cars won't have a hole to mount an engine driven fuel pump, which means you'd have to use an electric fuel pump, even with a carbureted setup. It's not the end of the world, just one more thing to set up. If you're planning on keeping the fuel injection, then it doesn't matter.

 

A 2 bolt block is fine.

 

Lets take a step back here. Is the car running now? Does it NEED a new engine? Puking a bit of blue at startup can be as cheap as $40 to fix for example. No sense dropping upwards of $4000 just yet.