Distributor advance springs

My understanding is "225R" is simply 225 regular fuel, & yes, the forged crank was phased out during the '76 model year mid-production. I also stand corrected, '67 and up South African market 2bbl Slantys WERE painted orange, if You somehow managed to obtain one. It's possible the "E" was dropped once the switch to cast cranks was well over with, but that's a wild guess, and reading what a "Wild West" the stampings became late '70's and up anything could be possible.
To be sure tho', the rods, & mains are different.
To add, the '79 and up engines also use a different Cam bearing set, due to feeding the Hydraulic tappets.