I am not sure what it is for sure. I think its an old F1 maybe Econoline. Hopefully someone here can pin point it. Spring center to center measure about 32 3/8 inches. 2751 is stamped on the wheel cylinder. That number crosses to late 60s-early 80s f250, f350, econoline. I don't know if that identifies the axle though. I am hoping I can use these brakes on my 32 Tudor. Haven't measured for any of that yet though. Thanks!