No, no and no.
1. There is (was) no big block or small block Pontiac. The same basic head and block casting was used in displacements from 326 to 455 cubic inches.
The capacity was varied by bore and stroke changes.
The 400 inch engine has a bore of 4.12 inches and a stroke of 3.75 inches.
Hence, I can change the crank on my engine to the 455 crank to increase capacity.
2. The valves covers say 'M/T'. This stands for 'Mickey Thompson' who, in his own right, tuned and built Pontiac engined cars in the 60's, one of them being the quad Pontiac engined land speed record vehicle Challenger 1 which achieved 406 mph.
Additionally, Thompson had his own speed parts company producing various tuning parts and a range of drag tyres. The company produced a range of M/T logoed valve covers for engines from the Chrysler hemi through Ford and Chevrolet engines to the dear old Pontiac V8.
3. Ford
Chevrolet small block (ten a penny), Chevrolet big block (a better choice), Rover / Buick ali V8 (for Land Rover owners only).
At the time of deciding to build the Dax, my wife drove a 70's Trans Am. Sadly, the body work rotted to a state where it was not worth repairing. However, the car had a perfectly adequate engine and transmission.
Hence, I used this for the Dax.
As stated by Randy, the Pontiac V8 is known for being built like a brick sh*t house, with bigger mains and big ends than the equivalent small block Chevrolet, has better head / port design and is capable of producing huge chunks of torque in a very broad band from pretty much off idle (which, as we all know, is what really makes a car move along the road).
QED
(ps, my wife now drives a 2000 Trans Am - this time powered by a generic General Motors LS1 V8 - a good 'modern' choice for a donor engine).
