Thanks for the info. I'll be running stock manifolds. They seem to fit by the power steering just fine.
I'm not worried about keeping it looking stock. So aftermarket floor shifter will work.
This will be a long distance driver for me, GA to OH every September. I was considering a 383 from a 66 Polara at a local yard to alleviate the firewall issue. He was willing to let the car go for rather cheap. But I'm not not sure I'm willing to drop to 14 mpg for the long hauls.