same on this end... I store my BH77 on a custom made pallet (maybe 3'x5') and the L3301 w/ forks is just (an I mean just) capable of lifting it a few inches off the ground to move around my shop. I usually have a 470# logging winch on the back and this as a counter weight still makes the back end very very light and front axle spec'ed overloaded.FYI, I couldn't lift my bh77 with my l3901 and forks. I had to lift/drag it off of my utility trailer. It's 850lbs, plus A LOT of wood in the transport frame.
I did my own install too. Definitely get metric taps to chase the mounting holes for the subframe bolts. Mine were badly powder coated.
And in terms of hooking it up to the tractor, yea hook it up hydraulically, and you can use the bucket to move the subframe pins. It's too low on the crate to do this the first time. I used a floor jack to raise up each side and throw 2x4s or 1x until it got close to height. I might even have used planks from the transport frame.
Build a dolly for it ASAP (essentially a big furniture dolly, look on youtube). Comes in SUPER handy.
I really only do this to rotate the BH so I can drop the winch and back into the BH for mounting. The BH is heavy built and itself makes a great (somewhat expensive) counter weight. would never try to move without significant counter weight.