I used K-Line 36" 2 RL wheel sets to convert my Trainman passenger cars. I reused the T'man truck frames. Don't remember if these wheelsets dropped right in or if I had to some fitting -- as it's been a while. But, it wasn't difficult and it worked out great. Put Kadees on too.
A while back I was able to find a large quantity of K-Line passenger trucks in blister packs on Ebay and bought them up. Both versions; 3 axle heavyweight passenger trucks and 2 axle lightweight passenger trucks. Got 'em to primarliy convert K-Line 21" pax cars. But, have used them on lots of other cars, too. Like GGD passenger cars.
Off topic, But, Atlas O now has a line of narrower, more prototypical 2 RL trucks and wheel sets with product numbers #7064 thru #7069. I was able to get about a dozen sets each of #7064 2RL 50 Ton Barber Bettendorf and#7066 2 RL Andrews trucks. Atlas O introduced them a while back and produced some. I see them on Ebay in small quantities from time to time. I'm suspect they are caught up in Atlas O's production problems?
And the previously offered wider Atlas O 2 RL trucks and wheel sets are still out there too for our use. So we have the choice of older wider trucks/wheels or the newer more prototypical ones when we can find either versions.
AG. great method of narrowing the older style Atlas O truck frames. I have a bunch of Intermountain 2 RL wheel sets that are of course too narrow for the olderAtlas O truck frames. If I run out of options with Atlas products I will give it a try.