Fwiw, I've got about 1k into this mess, so I'm money ahead compared to buying "correct " parts. That includes a couple extra carbs and rebuild kits for them.

I really really wanted to use the 350 I have for the center, mainly because the main body is just a little smaller. But, turns out it's worth what I paid for it, zero. Pulled it off a junkyard truck that had been sitting without a hood for a long time. Just rusted solid.

So, 3 500s is what I'm going with. Bad idea? Absolutely. Way too much for my current engine.

But, I'm enjoying the challenge anyway.