The timing chain cover is the water-pump housing on a 305 - this will fit your 478M - you will need to plug the balance shaft oil holes under the cover/ change the timing gear/chain set-up - the crankshaft/flywheel switch over is where the problem/expensive part comes into play. The person to contact on here would be BBV6 (Pete C.) as he has done this engine switch. From my experience on these motor swap/improvement would be a 351 of some version - far easier and less expensive with a good improvement.
