The good news is that the 720 has it's steering box on the outside of the frame rail so there should be lots of room for just about anything. My 710 (Violet?) has a KA24E 90 amp. alternator from an S13 240sx. I had to swap the V belt pulley onto it and add a small spacer on the shaft so it wouldn't rub the case. Stock belt was kept. Made a nice connector for the two wires. This connects to the stock harness and into the new alternator...
I did not trust the stock 14 gauge wire to the battery to handle 90 amps so I made this 12 gauge and ran it to the starter lug so it could get back along the positive battery cable. Every thing soldered and heat shrink tubing and then covered in 720 harness protector and covered with electrical tape.