That's one reason I recommend doing the 5 pin ECU wiring. Parts availability. With stock stuff, even if the parts store doesn't have it, a pull a part might. I don't think I've bought a new ECU, voltage regulator, alternator etc in years. I just grab used ones when I find them.
Been 40 years since a 5 pin ECU was used, finding a good one in a yard is a long, long shot.
No one sells working 5th pin ECU's and if you find a new one with a 5th pin it's a dummy pin.
While it could happen that the need may arise the odds are you'll win the lotto first.
