Id check into a floor mounted pedal box for clearance before deciding to go with another motor, i think someone mentioned it before about trying a bottom mounted pedal but theres a lot of after market companies that manufacture floor mounted pedal boxes and most are designed around racing so they are smaller and take up less space. just my thoughts before possibly changing directions to the 312 or a SBC. My buddy is building a car from that era and since space is so limited id suggested to him about buying an after market box to save on space.