Having just wrapped up a B&M XM-1, and having three more on the bench, I have a few comments concerning the 71000-series cars:
The best visual match for the 71000-series trucks is indeed the Red Caboose Y-type. Downsides include the snap-together, "equalized" frame (although I have had some success gluing these to make them rigid), and the absence of brake shoes. I took a hard look at modifying the bolster to accept Kadee shoes, but threw in the towel. Game vs. candle and all that.
The Bowser 2F-D8 trucks have a different look, and perhaps are a better match to the PRR trukcs, As Ben noted, that depends a bit on which photo of the PRR trucks you look at -- thy were not all the same. The Bowser truck has molded-on brake shoes, although I have ground these off and installed Kadees with no difficulty. If you really squint, you may also notice that the Bowsers lack spring planks, but these can be faked by gluing two small slivers of cardstock or Mylar into the bottom of the spring box.
The Kadee 2D-F8s are, AFAIK, still only available sprung. No comment.
For the 72000-series cars built in 1930, the best visual match to my eye is the lovely Tahoe MW Buckeye truck. Very, very close to the prototype's side-frame profile.
Hope this helps.
Swall Meadows, CA