350 swap would be cheaper, but won't be cheap either. You can use your stock trans and gears, but if you abuse it it won't last, All the older 350's will work, But a better option would be a Chevy 4.3 v6, you can also go with a ford 302, then there is the 2RZ & 3RZ not to mension UZFE family of v8 and diesels.