Yes. You'll need the motor mounts from the donor vehicle. Also, the exhaust is different.
Yes.
the block & heads are the same you just have to pull the 305 out & put the 350 back in
yes you can swap the 454 for the 350 its compatible usually any Chevy engine will match in the same vehicle might have to do sum fabrication but in ur situation you should be fine
Everything
250 to 350 hp depending on what model
As long as the 350 is a fuel injected engine / TBI / Throttle Body Injection engine there is NO difference.
Which 350?? Chevy or Pontiac? A Pontiac engine will drop right in. A Chevy takes a lot more work.
NO.
the g20 should be a 350 and I believe the caprice is a 305 you can swap the engines but you will also probably have to swap the intake and exhaust manifolds
No. You will have to get v-8 mounts.
easy, take out the old engine, and put in the 350. it really is that simple.
The frame engine mounts need to be moved and the headers need to swaed with the 350.