Purist or not you should also consider what it will bring down the road. Most Chevy fans won't like it because it is a Firebird. Most Pontiac fans won't like it because it has a Chevy motor.
Hokie brings up a good point here. The potential customers for the bird is far fewer if its had a soul transplant.
And your right you will need to get a new motor mounts. Hard to say on the wires. There were differences between the chevy and Pontiac wire harness. Your may have been modified to work??? I think they run about $150 each for the two.
The only downside I see with going back to a pontiac motor is they are getting hard to find and may cost a bit more $$ to swap. But in the long run IMO its a better way to go.
