1974 Columbia/Harley Davidson D4E

[Teitup2]

Both diodes at the back side of the speed controller check bad. It seems near impossible to find a parts list for this year (1974). Some of you out there who are a lot more knowledgeable than myself might chime in and get me on the right path. I think I need a parts list for the year OR if someone could help me with the part numbers that would be great also.
Trying to save this (looks like new) old cart.

Looking here the guys have most of the years covered just not for 1974 electric.

Thanks in advance to any of those who could help me.

Steve