If you go with the 4.8 i believe the liters to be, small block 8 you wont have any trouble at all. it's a pretty simple install as far as engine swaps go.

Your whole front end will come of in essentially one large peice with the removal of I believe around 5 main bolts and few other miscilanious small ones. You should check out www.s10forum.com there is several on there that have done this swap to theres.

If you try to go bigger than the 4.8, say with a 350, you'll have some serious cooling problems. the 305 would work much better and there is a ton of upgrades for the motor available. you can easily push 400 pluss on one of those.

I know a few people that had the 350 swap and they had numerous problems with trying to keep it cool enough in the compact bay of the s-10, one had to have a full custom radiator just to keep in from overheating.

Is your truck setup for a stick or automative right now? I don't remember is the 4l60e is a auto or not. I would recommend that you go with a stick setup though.

You should be able to find it on the s10forum.com there is a guy on there that found a company that will take your stock computer/wireing harness and mate it with the computer for whatever engine that you choose to use. That way you wont have to change out all your gauges, you can use your stock interior gauges and such.

Hope your project goes well. and have fun.....