Found a great site on the Buick 320:
http://www.roadmachine.fi/Buick/Rmaster.html
Chev Rat valves, Chev Mouse springs/retainers, bowl ported, headers, 2*2v (EFI?) intake, 7.6 compression
Didn't mention any cam change or bore/stroke:

1946 Roadmaster 320, 2.73 gears:
19.53 at 72mph in the 1/4 mile