That does sound cheap, I did the calculations in my head and came up with 289.24. ;-)
I built a supercharged 302 years ago and just grooved the heads and torqued them to 120ft lb. This crushed the head gasket in the head and cured my head gasket problem. Ford 302 has only 8 head bolts and they hate boost.
I would think you'd want to go with a smaller looser converter considering the weight of the car and the need to build boost. More of a question than a statement.
Should I focus on a 64 225? One more thing, you haven't mentioned compression ratio?
Hope you got a light driver to complement the light weight seat and rug 8-)