I seem to recall The wood boards are not interchangeable At least some have to be different I have both styles and I rebuild a 50 and wasn’t able to use any of the 53 parts when I fixed my 50 1 ton In the end I cut new boards from 2x6 or 2x8s and left them full thickness except where the cross sills were located and I trimmed them thinner to fit to the factory surface This way the wood was a full 1.5 thick where ever it wouldn’t matter in the middle of the floor planks -s
