I have ran mine once. It ran good but I was plagued with clutch problems and my motor mount wasn't stable enough. I would consider my build a fairly mild one. Isky 246 .330 cam, Raceseng S2 flywheel, billet rod, ported head, champion rockers, stainless valves, Mikuni 34 flat slide on alcohol. I had mine mounted to a wing outlaw kart. I would say it makes around 30 hp and it has a lot of torque.
Burris's big block adapter plate fits on top of the angle part of several mounts, that is what I used too. I don't like the multi piece mounts. because as the frame flexes and twists so will your engine.
The new engine has mount holes about 1" farther apart front to back than the standard 390/305 big block mount. I spoke with Geoff about this and he said they had done their testing using a two piece mount as mentioned above. I don't think the 2 piece mounts are strong enough to hold the torque applied to the engine base. These things need as much support as they can get, if you ask me. Anyway, Geoff said he can manufacture a plate to fit a PMR mount like what NR sells to adapt to the new engine. I was in a hurry and ended up fabing one up myself out of .200 aluminum, which I then had to use another piece as a spacer to save some time in machining counter sunk holes, etc. My mount was not rigid enough partly because I had it offset so much to fit beside the seat. I'm actually considering welding another motor mount tube on my chassis to get the mount "under" the motor better. The gen2 440 is a beefy piece and almost everything is bigger, this is just one of those things we have to deal with when going that route. I'm sure Geoff will come up with a plate for us. I personally would recommend a .500 aluminum billet motor plate.
We just tested ours last weekend and lets just say, its a force to be reckoned with! Noticable power increase over our similarly built Predator 420 and the price cannot be touched considering all of the extras that are included with it.