400 or 455 swap into '66 Lemans
From what I understand, all Pontiac V8's from the 326 to the 455 have the same outer dimensions, but would I have to change anything if I swapped a 400 or 455 into a '66 326 car? Motor mounts, etc? I'd rather have a 389 or 400 but I'm leaning toward a 455 since they're bigger AND cheaper.
The trans is a 2spd, probably an ST300 but could be a Powerglide. I know they worked okay behind a 389, but it's the original trans with 180,000 miles on it and I'd much rather have a 200r4 or TH350.
And finally the rear end is most likely a pegleg, and I want posi. Would a later (68-72) rear end work?