Thanks for the FI information. I had toyed with the idea of doing this on my 250 after seeing Clifford Performance website, but decided to keep the Clifford/Holley intake and 4 bbl setup.
They say that getting there is half the fun. So, I've ruled out GMC trucks/engines and have decided to go with a '55-'59 Chevy instead, with a 261. The '60 passenger car will have to wait. The good news on that at least is that there seem to be a fair supply of 235 engine blocks out there when I get around to doing that. I don't expect to find an Impala with a six in it.