Ordering a 1974 Engine Harness...not sure which one is correct?

[Canuck74]

Hi All,
I'll be ordering an engine wiring harness from Year One, as produced by M&H electric. The problem is, they have two different harnesses; one for cars built before Oct 12, 1973, and one for cars built after that date. I'm not sure when exactly my vehicle was built, as the data tag is missing from the door and the data plate is missing from the K-member. Will my build sheet give me a production date for my car? Does anyone know the differences between the two harnesses? The sales rep didn't know but mentioned something about 3 vs. 4 pin connector. I'm not sure which is which but I do plan on calling M&H.
Thanks in Advance!!
p.s. I've attached a copy of the build sheet in case that will be of any use.

 

[moparleo]

Try this http://www.genocide2600.com/~traviso/mml/bodydecode.html

 

[Canuck74]

I called M&H on Monday and talked to a sales rep. He described the difference as a change in connector about ~8 inches from the bulkhead connector. Early cars used one T-Connector for 4 wires, later ones used 3 wires into a T-connector with an additional wire and connector. The sales rep did not know, but I am assuming this is for the Emergency Seatbelt Interlock Override switch. I have seen 2 possible different override switches, so my presumption is that it is for one of the two different switches, although I'm not sure what the connections look like on those.
I went with what I believe was a build date on my build sheet of 8/22 and the fact that it appears to be a very early build car
JH23G4B10---- (less than 7000) and ordered the early one.