I bought an MD Juan tub for my 3B about 4 years ago.
Just about everything fit.
Yes the trans tunnel was off but only about a half inch. I could deal with that by just opening up the hole a little.
Original fenders mated to the tub with only a little adjustment.
Of course you have to cut all the dash holes and the foot pedal holes in the floorboard.
There was NO hardware with it. We re-used the passenger seat hinges, tail gate hinges and windshield pivots from the old tub. Also the outside rear view mirror mount. Probably more that I don't remember.
But having read many stories of very bad fit, I was pretty satisfied with how close everything fit.
I would hope it's been refined even closer in the years since.