Karl, as per the Judging manual "Front bumper, over-riders and support springs(support brackets). TR2 & TR3 bumpers and overriders are different from the TR3A &TR3B. They are not interchangable. Rear bumpers are the same for all models"
MOSS MOTORS has a very definitive listing of commission numbers and model numbers on page 3 of their catalog.
Hope that helps.
Tinkerman