Thanks!
Pretty happy with finding the NOS blue Pettys, nos Petty HEX grips, original Yamaha rims etc.
About the fins, I did it solely because Eric Cheney did so on the engines back in the day.
Same with CCM.
It's said to stop mud clogging the fins, if you look at a engine made for MX it's usually a pretty big space between the fins, a street/offroad XT500 or B50 it's not.