[Mart]

I like those original nuts that were a bigger hex size. I had just the one on a 40. I'm not sure which years they came on though. Standard hex size is 15/16" for a 5/8 nut, there are bigger, something like 1-1/16" (guessing here). Like mentioned above, saving the original nuts is a must. That said I have used aircraft quality self locking nuts (Philidas brand) on my roadster and I like those.

Mart.