I have the WVC35001, 1/35th scale Canadian Ram Mk.II Series 4 Kangaroo from Friendship Models in 1/35th.
See also their FaceBook page for more info.
My Measurements here.
Designed for the Academy M3 Lee/Grant. For Shape, I like it better than the Bronco.
I also have the Academy 13228 M3 Grant, “El Alemein 1942” Special Edition.
This has two sets of Bogies, early & later, allegedly including the ‘corrected’ early, I haven’t measured them. This also included the major interior parts.
The Bronco CB35215 RAM Cruiser RAM MK11 early, which has the early Bogies & “H” pattern track, not CDP track and NO interior, as you note.
What you intend is certainly possible, and there have been recent builds (on TwitFace probably) but I can’t remember who or what base kit they used.
Resicast also do a RAM conversion.
Marcos Serra’s blogs are also worth a look.
As you intend/have to kitbash anyway, the Friendship/Acadamy combo may be a better starting point, & keep the Bronco as an OP tank, which did serve in the ETO.