You are on the right track with your "looking factory" appearance theme. A car that nice with apparent numbers matching should stay that way.
What a fantastic sounding car.
You should get the PHS docs for it too.
To run the #48 heasd you will need a dish piston to lower the CR a tad.It will be too high for pump gas. Pistons with a "D" shape would be the best option .
Your build is totally within the bounds of reality.
Also with the 4 speed you have, It would be a plus to keep it. You should ID which one it is. If it is the close ratio trans, that would be best. Pontiacs make lots of torque. A low first gear will probably not benefit you in that respect.