Sounds like a propane burner might have just the right temp range and the portability you are looking for.

Build a box around the part and use a propane space heater over night, then use large heating torches. You should be able to rent the heating torches. Be sure to measure the bore and allow some clearance before trying to fit over the shaft. Check the interfearance of the 2 parts when cold, be sure it can be heated enough to allow installing clearance. The Machinery Handbook can help with the calculations.

a box made from old firebrick or ceramic fiber and a cheap ice-melting propane torch from northern tool(500,000btu) will do the trick quickly and easily.
we keep a setup like this in our home shop just for such occasions.
in the foundry, we just use one of out heat treat furnaces.
bobc