Pretty close to bolt in; you have to change motor mounts but the trans stays in the same spot so driveshaft length is the same. Even the 4.3 ECM and wiring will work; you just change the PROM chip.

A friend gave me a 307 short block with a new set of rings and bearings and the block machine work done. His kid was rebuilding it from a 68 Chevy truck he had and lost interest long ago. Not exactly what I planned on but for the price, I'll take it and use it. I'm just going to put on a set of home ported TBI heads and intake along with a cam upgrade and call it done. That's about as cheap as it comes.