Taper pins. Yes, I've found it very variable. I ended up with some 1/16" pins from two different suppliers. One lot was very tidy, the other was a mixture of OK-ish and rough. The good stuff came from EKP Supplies www.ekpsupplies.com 1/16" x 1/2" Taper Pins Qty 10, about £3.50 I think. I only got the reamer from Tracy Tools, sorry if I didn't make that clear. Wider pony truck frames? Depends how itchy your hair shirt of authenticity is. You'd have to make quite a few new parts to do that. You could compromise and just put some extra profiled plates on the outside of the frames to space the spring castings out. Honestly, I don't think it's worth the effort.