I agree with Ralphy. Keep the '54 - the insert bearings and the improved oil system (and higher oil pressure) are worth having.

Ralphy refers to "rod bearing maintenance" on the babbitted rods. One trick I learned when working in a shop in 1970 was when the rod bearings reached the point that no shims were needed (measured using plastigage), you could get a little more life by filing the mating surfaces between the rod and rod cap to make a tighter fit against the crank (he called it a shade-tree trick).

Tim