An 8 foot 4 X 4 post across both windowsills with the doors open gives you room to manipulate a cable come-along to remove and reinstall a SM 420 without crawling around on the floor and trying to balance the transmission case on a jack. Just bolt a chain to a couple of top cover bolts and hang the transmission on the chain. I've actually done that when replacing transmissions and/or clutches on conventional cab 18 wheelers with transmissions weighing several hundred pounds.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!