Well I might as well put in my $.02. I had one "back in the day" in a 48 Chevy coupe. Of course then you could buy speed parts for them. IIRC I got some about 9.5/1 lightweight pistons, a Racer Brown roller cam and lifters, cleaned up the ports of all the nasties, The valve sizes escape me now, but they were larger. Then the bolt on stuff. I fabbed up an intake out of tubing with a box and drilled and tapped it for a Carter AFB. Also fabbed up some tubing headers. The trick was to build the complete flange and when everything was set up to bolt it to the head and weld up some 1/2X1/2 to it just to hold all the intake tubes and conversely all the exhaust tubes together before cutting it apart. The only downfall I experienced was not having a high volume oil pump. If I pumped up the pressure it would wash the bearings and if I left it alone it would beat them to death. Lots of fun back in the late 50's and early 60's. I'm sure when Proffitt gets back he will have all the new tricks. Or maybe go to the Inliners board. They have some GMC type gurus there.
Regards
Dennis