I'm not aware of a course spline aisin. I believe they started in 75ish with the disc brakes and fine spline. There is a difference though in the body length of a 75-78 aisin and a 79+ due to the birf length. Since the aisin hubs only came on 55's from 75-79 they are somewhat rare. The latters are dime a dozen since they are the same as a mini truck, 60 etc.
All 40's had drive plates from the factory with dealer added locking hubs
All the 55's came stock with aisin hubs with disc brakes from the factory 75+. I'm not sure about pre 75 but I would assume they came with driveplates and then got either selectro or warns from the dealer.
See you on the trail
Couple o' FJ40's, BJ70, PZJ77, UZJ100, TDI