Pennsylvania Railroad Expertise Needed

There were very few torpedo K4s - one of the one model, and 4 of the lesser streamlined model.    And they or somemay have lost the streamlining in WWII to save metal for the war effort.    

The fleet of modernism were light weight cars obviously and newer.    I really don't know for sure, but I am going to guess that they stayed with the long distance named trains.    

An express train such as you running would have coach accommodation, but I think it would be older equipment like the heavyweights.     These trains probably did not run on convenient people schedules, they did not need to.    Therefore they probably did not see a lot of patronage.      This is just sort of random thinking about  your quesion.

Certainly it would not be wrong to stick with heavyweights.   

The engine you have is painted in a 1920s-30s paint scheme that was probably gone by time the LW FOM painted cars arrived in 1938 (these were PRR's first LW cars).

As far as K4s pulling LW cars, I have several PRR books and I could not find a single picture of a K4 with LW cars.  They were all HW.  That being said, in 1938 the K4s made up the vast majority of main line passenger engines on the PRR.  The S1, the first of the big engines, was still a year away and the T1s were three years away.  So I think I can safely say the K4, probably double-headed, pulled the name trains with the FOM cars. These trains may or may not have any head-in cars.  If any, probably one RPO or B50b.

If you are looking for something prototypical, I would take off the two passenger cars you have and add a Lionel 6-15558 HW car as a rider car.  The 6-15558 is  Lionel's standard HW coach but with 4-wheel trucks instead of six.  It also does not have the PRR passenger three strip scheme that came about in the mid-40s.  This nicely simulates a P70 coach that was often used at the end of express trains as rider cars for PRR employees.

If your K4 is the torpedo, it pulled the Broadway with streamlined, FOM cars. If the other streamlined one, it pulled the Jeffersonian with remade PRR P-70's in a pseudo streamlined look, painted FOM. Eventually, it pulled ordinary P-70's. I cannot recall how long the Jeffersonian streamlined shrouding lasted.

John Daniel posted:

Please advise whether I should stick with heavyweight cars, and if not, whether the Fleet of Modernism cars and/or some other 18 inch lightweight Pennsy cars would be appropriate in this consist.

       

I think either way would work, check this one out;

[this screen shot from locomotive-wiki

https://locomotive.fandom.com/...ing_Broadway_Ltd.jpg

and as such is licensed under the Creative Commons Attribution-Share Alike License 3.0 (Unported) (CC-BY-SA)]

These two videos show non-streamlined K4s pulling cars from the 1938 Broadway limited train consist: 

https://www.youtube.com/watch?v=MOXV_uAJxfI 

https://www.youtube.com/watch?v=7FzWh3Sqhnw

Oh, here i thought you were talking about the "torpedo" locomotive. My mistake, thats what i get for "skimmimg" the post and not really reading it through.  Where your model does have the "early " K4 tender paint job,as mentioned above, it is your railroad to operate as you wish. 

Those vids posted above this post are some of my fav's of PRR K4's 

There was one K-4 that never received the front end "beauty" treatment. If yours is the "basic" K-4 you can use it with whatever you choose.

There were 2 streamlined K-4s pulling "Fleet" (1938-48) cars. The "famous" Loewy design engine only pulled the Broadway Limited (along with regular K-4s on occasion). Then there were the 4 K-4s that pulled other "Fleet" trains, like the Jeffersonian. These were designed by the Altoona Shops, and IMO, are better looking than the Loewy design. The only "O" model of this engine is a Williams brass, which I have.