i have a 75 400 that I am doing the same to right now...most tell me its not going to do this or that.. compression to low.. I took a measurement and came up with the piston being in the hole 37th.total.. I have a old crane cam hyd. I think its 504/528 something along that line with a 112 plan to install it at 106 or so..i have a tm6 intake and a 750dbl pumper carb..will run a 727 with a 28/3000 verta and 456 gear for right now 70 duster frame conn. ss spring,mini tubbed, oh yea I plan to put some nos on it as well.. this will be my street car/toy until I finish my chassis car...hope it will be in the 7xx in the 1/8 mile but who knows...