There was 6 different types in all. The M36 set up, was supported by three poles and was "free standing" over the canvas top, independant of the cargo bed.
The M23 and later M37 (in its 4 different versions) had two steel square sections for uprights with gussets in the underside corners, and was "attatched" to the front end of the cargo bed.
The actual ring (M49) was used on all configurations but the ring support structure varied, between 352, 353 and wood or steel cabs and / or bodies.
There were of course field mods from salvaged kit, but we're talking factory fit here.
I'd post some pictures for you but regret I dont have a hose at the moment.