Still would not use the original 400 block.
Would go with either a 455 block or a 400 block with all 5 motor mount bolt holes. But NOT a "557" block.
You can put an electric choke on most any carb, including a Q-jet.
Butler sells a ready to assemble short block kit. They supply the machined block. Have to add over $500 to get a forged crank. I'd go with a stock 455 crank before I'd use a cast Chinese crank. But if you use a 455 crank, you'll have to use either a 455 or 428 block.
https://butlerperformance.com/i-3164...tegory:1459600
Looks like they've had a recent price increase. Looks like going the Butler route, plus alum heads, it's gonna take nearly 10 grand to build your complete running engine, unless you know some cost saving corners you could cut. Is that within your budget ?
Since you live in NJ, you may wanna check with Richie Hoffman. He's built lots of strong Pontiac engines. I think he's on Long Island. He's a member here.