Randy,
The 454 heads are door-stops. The 396 heads are a bit better. The best oval port heads are the '68/'69 350 HP 396/390 HP 427. They have the large intake port with the "open" chamber.
Installing the BBC in the T/A will "fit" using Camaro parts, as you alluded to. However, due to the extreme weight of BBC, handling will be destroyed. It will no longer drive like a T/A.
For the same money, one could have a 461 Pontiac, based on a 400 block. Weight would be right for the car, and power is at least as good as the BBC, if not better. BBCs aren't "rare", but they aren't "cheap", either. It's not like building a 350...
Jim
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