I mounted my engine with engine on its side on the bench mostly supported by a soft plastic 4L can and thick wooden plank. NOT all the weight resting on ign cover!
Wrapped the frame around it with help of my wife.
EDIT: Bolted most of the bolts so frame could be moved with engine NOT wiggling around in it.
Later my friend arrived and we both took it down on the floor on piles of wooden planks, jack stands. Then easy to mount fork, wheels etc.
I had to switch swingarm later when the chromed one did not fit. Bike on jack and jack stand
Back in the days I pulled the engine and put it bacl again by wrapping it out of the frame, bike on its side. Important to protect frame and engine to avoid scratches.
I had thoughts about taking out then engine again. (I did the frame kit job so I could remove head without pulling the engine.)
Like this:
http://forums.sohc4.net/index.php?topic=102658.0Bike on dollies, on for each wheel plus on dolly for side stand.
http://www.kotulas.com/deals/kotulas-favorites/less-than-50/snowmobile-dollies-set-of-3-1500lb.-capacityThen easy to move the bike when engine is hagning on the metal beam supported by jack and jack stand.