do you have any links to the build and how you adapted the box to work? Are you using the original transfer gears or a chain/belt drive to the input shaft?
I have converted a 77 moke and successfully kept the original transmission. It works but it was a pain to do and the gearbox is noisy and I'm always worried I'm going to destroy the 40 year old Leyland gearbox /driveshafts with the new power.
If I was to do it again I would look to drop in an imiev running gear or maybe fit a rwd cars diff to the front and belt/chain drive it with the motor sitting on top of the diff.
I fitted a couple of these "beam axles" over the years and it made the rear end of the mini very skittish, hence why none of the race series currently use them.With my old mini decades ago I threw the rear subframe away - instead I used a single bar across the back that carried the rear swinging arms and used coil over shocks with some reinforcing of the rear shock mounts - not a lot is needed the shock absorber peak loads are already higher than the spring peak loads
This gets shot of a rust monster and will give lots of space