most people use a 390 flywheel, but i havent figured out exactly what clutch to use yet. ive heard 400 12" clutch but dont know if flywheel has to be redrilled for that. wondered why not use 390 clutch. went to engine shop this morning and found 12" 390 clutch for about $275. dont remember name brand but started with p. will see if it works. one book i looked at showed same part #s for Centerforce 390 & 400 clutch, but different #s for factory clutch with same specs. hope somebody jumps on here and clears up this mess.