Motorhome carb size?

BWDart said

I have a 650 spreadbore which was on my 318 with a 360 spreadbore intake, it ran ok but when I replaced it with a 600 squarebore it runs many time better, better response and alot more power. I read where the holley spreadbore doesn't have a transition circuit coming off idle. Is that true?

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I really don't know the answer to that question, sorry.
I do know that the stock Mopar intake isn't going to make good power with a spreadbore carb as the bores aren't the same, and the adaptor will KILL performance.
It will, however, make a LOT of torque on a stock Chevy iron intake. If you already have a spreadbore Holley, drop it on and try it! Ya have nothing to lose!

George