Nice work on those trucks. I wonder how much additional work would be involved in tweaking them to replicate the trucks used under the helium cars. Attached is Jay Miller's handout that has views of the various trucks used in the helium fleet. The biggest difference I can see is the size of the journal boxes. The He cars rode on 6.5 x 12 journals and the boxes are visibly large. A second difference for the early cars is the Andrews bracket as the journal boxes were demountable.
I'd be curious to know what your thoughts are having been down that road.
