Jeff, Sorry for the longwinded reply, remember I have a 422, not quite as much height as yours.
First helf for the LM Bucket 24 ins deep, upper shelf for Forks and Mini-hoe, 36 ins deep.
Height from floor to upper edge of shelf 29 1/2 ins.
From that point to the same point on the top shelf 22 1/2 ins.
Since 2 x 4's are 3 1/2 ins that leaves 26 ins for the Mower and 19 ins for the LM Bucket. My lift and tilt limits are just enough to allow me to insert and secure the adapter plate into either unit.
Lot's of luck, install plenty of good vertical support, and learn to treat the operation as if you were handling a baby, these P T's are powerful monsters.
Bill