I wonder if when the PA was made, the same long wheelbase trucks were utilised as on the DL109. I also wonder who made the trucks as they were apparently found on some FM locos too e.g CPA24-5, Erie builts. This would surely make maintenance easier if all these trucks were interchangable. I am sure I will be corrected!
Interchangeable? Are you suggesting the railroads should STANDARDIZE? ... It might have been a good idea, but the corporate/industry culture of the time didn't go that way.
The A1A trucks used on the Dl-109 and the PA (and also those on Baldwin's 2000 hp passenger locomotives) are very similar in design, but not quite identical: the PA's truck has 2" longer wheelbase than the Dl-109's. (I have read that this is connected with Alco-GE's decision to offer 42" wheels as an option on the PA instead of the usual 40".)
The rear trucks on 5-axle FM trucks and the cast-frame trucks used under Erie-builts are similar (similar enough that Doyle McCormack is using trucks from scrapped Erie-builts in restoring a PA), but slightly different: the top of the truck frame is a flat horizontal instead of the slightly inclined angle of the PA and Dl-109 frames. I have no idea why.
I'm not sure who made these trucks: truck frames are large castings that the locomotive builders bought from outside suppliers. Commonwealth Steel Castings was one supplier, but I don't know if it provided the castings for some or all of these locomotives.
(Note that even identical-looking trucks may not be exactly the same. Apparently -- this from Preston Cook's articles in "Railfan & Railroad" -- later models of EMD E-units were heavier than the earlier, and had somewhat beefed up truck frames to cope.)