If my experience with McLeod diaphragm clutches carries over, the pressure plate fingers need to move about 3/4 to 7/8” for clean shifting. Add something for free throw and you are looking at about 1” for TO bearing travel. You can bench assemble the flywheel, disc and pressure plate on the bench and measure the stack height from the flywheel-crank flange to the fingers. Then mount the bell housing with a couple of bolts on the engine and measure the bell housing effective from the crank flange to the transmission-bell housing face. Subtract the first from the second and you have the distance from the clutch fingers to the face of the transmission. Then you can play with the TO bearing dimension and TO bearing retainer dimensions and see how much room is left for TO bearing travel - it needs to be around that 1 inch or more to include some free play.
The 1.25” flywheel versus more typical 1” thick flywheel may be the problem but there could be some other issues too.
On GM cars I usually use an adjustable height fork ball pivot to optimize the fork position and travel. I guess on a Mopar you can do the same to some extent with shims under the pivot. All aftermarket manufactured clutch’s height and flywheel thicknesses vary all over the place. You can’t count on any of it to be a duplicate of the OEM pieces anymore. And going from a B&B to a diaphragm pressure plate adds to this, although it can be adapted. For this reason it’s always a good idea to do a lot of trial mockup with clutch, flywheel, fork, TO Bearing and linkage install on the bench and then the engine before trying to mount the transmission.