If you want it original , put the 350 back in, if you just want a nice 'looker' add the 400 hood and keep the 400 motor.( or add in a 428,455).I have 69 conv. 350 that former owner put a 400 in ,just getting my newly bought used 400 hood painted to add to car. ( and if you want a used 350 hood in great condition ,now red,next week mine will prob. be up for sale)