[north]

TH400 codes for fullsized cars:
400-290 & 265 horse: PB
400-340 horse: ?? (I've never found factory documentation for the trans code for this engine (it was a mid year introduced 4bbl engine option)
428-360 horse: PA
428-370 horse (police): PH
428-390 (HO): PC

While most variations between these codes relates to different internal components in the transmission to better suit engine characteristics sometimes you can have two different codes where the only difference is the speedo drive gear teeth count to reflect the standard axle ratio difference between two engine choices. I don't know what are the differences in the above transmissions. btw, the 400-340 engine was a four barrel version of the standard 400-290 standard engine. Both were high compression small valve and shared the same heads and cam etc. The 428-370 on the fullsized car was police only and basically the 428 HO without the chrome dress up or long branch manifolds. In other words it used the same 62 heads, 067 cam, carb, distributor and 4 bolt main bottom end from the HO. Interestingly the manual transmission version of the 428-360 was identical to the police engine while the automatic version used a two bolt block and the cam and small valve heads from the 2 bbl 400-290.

Grand Prix transmission codes:

400-350 horse: PW
400-265 horse: PT
428-370 & 390 (HO) horse: PR

The 428 370 (standard SJ engine) was very similar to the HO with dress up kit and same heads, carb and 4 bolt block but without the long branch and it used the 066 cam instead of the 067.

Grand Prix