The existing radiator on the '90 Monty is trashed-cannot be repaired.
Looks like the GEN II '92 + core width is the same. If the horizontal distance between the frame mounting holes is the same as the '90, 25 1/8 inches, I can make a GEN II radiator work. The hose connections are in the same places.

90 LWB RS: 3 L/mt, JBaker springs, bushings, swaybars. KYB shocks tweaked, 134k mi, original owner.
97 LWB SR: SOLD Sep. 2014 131,006 mi: running boards removed, BFG 31x10.5 AT/KO tires, Air locker, AirLifts, KYB shocks, Cibie fogs, 3rd owner.