So I got the 3B big valve + 5 speed from Joe Katana up near Dallas maybe 7 years ago. The reason I got this was because it had the 5 speed top cover for 40 series that was shifted forward. It had a splitcase that was a 34mm idler. I remember that it was an LX and had funky stripped colored...
If your new 5speed has ears on the retainer then it's the 85+ design. See the last 3 pictures.
I know one of my 3B 5 speed shaft came off a 85 BJ42 LX out of Netherlands.
Eitherway you have some part numbers to reference.
I agree that Georg is the man but I may have both types of B h55f shafts as George has converted those 5 speeds from B to the course spline F over the years.