50gal heater in the air. Advice?

Forgot to take a picture, but had a no hot water call at a dentist office today. 50 gallon power vent in a small closet up on a shelf above a floor mop sink. The igniter and pilot line had been rotted away from a slow leak from the tank. Great! Second floor, basically a one ladder/person room. I'm 6' and can look right straight into the combustion chamber. The shelf it's on is just big enough for the heater itself.

We're going to put a 40 in it's place it only feeds three sinks and a washer. Tankless Isn't an option because of a recirculation line.

Any tips on dropping the leaker and lifting the new one up there? No place to put in a chainfall. Job is Thursday, not looking forward to this one.

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