hotelcalifornia is correct in the design differences in the chassis.
As far as parts that will convert or will not convert... everything will convert from the standard Triton to the Triton Jr except for the following items:
-Rear bearing hangers and lube rings (Triton Jr only takes small/standard bearings)
-Left side tie rod
-Rear bumper/rear bumper mounting kit
-Motor mount (to accommodate smaller tubing)
-Body kit