When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The tracks are functionally the same. The 56 cab I recently bought the frame is angled a little towards the back I guess to accomodate the tank being in the cab.
Im not sure if they are the same or not however, if you are wanting to go restomod, any seat you purchase will be accompanied by a set of rail adapters that will allow the new seat to fit up and function properly. I guess what I'm telling you is that the rails wont matter get whatever fits as long as you know where they came from you can get the adapters for the new seat regardless.
i have a set of rusted up 56's in the garage and went and looked at them and compared them to the ones in my 53 . now mind you i'm blind in one eye and can't see outta the other but they sure looked the same to me . by the way i have an 84 ford truck seat i have to slightly alter the width of , but it fits where the tracks etc of my 53 are with just a slight alteration of the track on it .