Lacking power

I bought a 87 chevy c10 silverado 4.3 litre v6 about two months ago,and the first couple of weeks I had it the block cracked on me. So I got a friend thats a pretty decent mechanic to swap out everything in that truck to make it a 350 v8. It runs alright but idle is to low. He said
its going to be a little rough because of the cam he put in there.

But thats not my main concern. I raced a few 80s model chevys and they always get me bad. If I punch it the engine will rev up good, but the truck will hardly be moving! I know those trucks werent sooped up.
It just seems like somethings holding it back.

He left the air breather that was on the v6 on it which is smaller than it should be. Would that be cuase a big problem?

Oh and it still has the rear end off the v6.

Perhaps gearing??? What kind of tranny is in there? Stick or auto? It could also be the clutch or a worn pressure plate. If you did not change the transmission or the clutch, the 350 may be overpowering it, if it was worn to begin with. Mind, this is all assuming the engine is making power.

That's my two cents. Anybody else got any suggestions? Keep us posted on the progress dude!

I think Oceanoasis is dead on. Sounds like the tranny is slipping if its an auto, or the clutch if its a standard.

The breather may also be holding ya back, but I bet its something in the transmission.

Its an automatic tranny. Dont know the exact size of it though. I guess I'll swap it out as soon as I
can.
Thanks for the information fellas much abligde.