225 Modified Slant

I picked up a "Modified" 225, it came with a Clifford 4bbl. intake, a pair of headers (2 3 port) mated to an 833 4 spd. I was told the head was shaved and it has larger valves and had a 650 Holley when it was installed in a 68 Dodge short wheelbase van. Supposedly gave Camaros and Mustangs a good go from red light to redlight. Anyone else think a 650 is a bit much. Comments. I am currently preparing a 66 Valiant 100 post car to drop it in - no chrome - sinister looking! Just wanna know what size carb you slant Gurus suggest.