Yes, It does from 57-64 then 65-72 & 73-79, generally speaking and wheelbase for wheelbase & Model for model. What makes the 57-64 type frames so different is the 4 leaf springs, one at each corner, live front [single I Beam] axle, a Front X Bellhousing mounted engine, totally different steering linkage & location, different frame rail configurations & X-members etc. these frames are very similar only in the years 57-64.

65-72 are likewise similar in the 2wd versions. The 73-79s are close to the 65-72s, but a tad longer, and the rear rails a tad wider. Still a 65 & up can be bolted to a 79 or vice-a-versa by fudging the bed in CA area & redrilling bed to bolt down on the wider 73-79 rails.

But bolting a pre 65 to a 65-79 style frame, altho' it can be done is probably more work than most novices should tackle without a bunch of resources. Things such as experienced help, equipment, [welder, crane or body lifting ability] huge shop with a good selection of tools and so forth. It's more than a couple of weekends of work.

Oh BTW,Stepside is a Brand X terminology, do you have a brand X pick up box/ bed? If not, we call them flareside because of how tops of the sides have a slight flare.

FBp