Dodge / Plymouth 440-6 Vacuum Advance Unit 3514332 . . . WHEN was it used?

[BigSig 6 Barrel]

Like the title asks, does anyone have any information about the introduction of the 1970 electronic vacuum advance unit ... part# 3514332 ... as used on the 440/6 engines W/duel point distributor?

I could be wrong, but as far as I can tell, there appears to be one "older" style canister used on the early production cars ... a second canister used at about the first of the year > (approx. 1st of Jan.), and then the one in question ... a 3rd style ?, perhaps introduced sometime before the 71 models were released.

I ask, because I have one of these cars that was built April 8th, and want to install the correct dual points distributor back in it.

Anyone with an original 440/6 car might also be of help, just knowing which style you have together with build date.

The first photo shows what I believe were the 1st two styles, while the 2nd photo shows the canister in question . . . Thanks

[440ehigh]

It was used on 71 to retard the timing at idle to help with emissions.

What I've wondered since it was an emissions control. Was it mandatory on all 71 model 440-6 cars. Or did early build date cars receive the 70 style

[torredcuda]

`70 383 cars also had it, it was used `70, `71 and maybe `72?