I am pleased to report that the Lionel trucks that came on their new PRR GLa hopper are relatively easy to convert to 2 rail. In fact, Intermountain wheelsets are nearly a perfect fit.
The process involves removing extraneous truck coupler hardware and thinning the truck bolster.
Sorry, no pix to date. A full article on the conversion will appear in a popular scale magazine.
Other options include Yoder 2D-F8 or American O Scale 2D-F8 trucks.