R and U had the rails the same if we mean R400 and R600.
R700 has higher rail section and different front spring mounting brackets being removed backwards to accomodate longer hood (engine)
RD with RB also had higher section and fatter steel than a basic R but the same general frame shape. Same spread and lowering of the section to the front.
DM has its own frame style with its special front end (not like a R) and deep center behind the cab for greater capacity.
F model had its own frame, not similar to a R or DM.
RW2 together with MH and CL (not CH/CX) have their special chassis with "art" siluette of the frond rail ends looking from the side. Easy to figure out what I mean looking at any pic of a RW2 with the hood open. RW2 and MH also utilizes similar front spring mounting brackets, battery boxes together with front air tanks, fuel tank brackets and even the steering gerar setup. The front axles were also similar excepting particular load ratings of the beams and springs. Both had a standard higth of section and thickness (RW600, MH600) and larger numbers for RW700 and MH600 as an option. Aluminium rails could be used but those were bolted to the standard steel front section of the chassis.
CL frame looks similar at the front but spring mounts are different because of the set back axle relating to RW/MH.
CH is almost another story with straight rails front to back. Probably interchangable with Visions CX up to 2004 when Vovlo frames took the place.
RS700 and RS600 Western Valueliners (including Macungie ones as I got figured out) had their special chassis with constant section straight rails front to back. Could be aluminium as an option. Don't know the section higth and distance between the rails but suppose the last was the same as Eastern R's had at their back end.
RW1 Hayward together with WS Cruiseliner Western models utilized similar frames. The speciality was split design when the front part of the rails was an independent unit bolted to the pair of straight rails right behind the cab on a WS and below it on RW1. Another especiallity of those models was a steering gear mounted on the front axle beam, not the frame rail.
Don't know much about B-models excepting their frames had nothing common with a R and there were different desgns depending on load capacity. Too probably some other models of Macks of those years utilized similar frame style. Can tell H63/67 were different but nothing above it.