The trans mount bolts are exactly 2" farther forward. You need the bellhousing bolts, flex plate, converter, dipstick & tube, block plate (thin plate between engine & trans) and the shifter. The AOD yoke should fit the c-4, and the driveshaft should even be the right length! For good tranny builders, try
www.artcarr.com, www.levelten.com, hughes transmissions for a couple. For that power, you'll need the gearset with the extra pinions as well as the normal hd clutches etc.