Another alternative is to use a burner (or perhaps two for a big job)
from an oil furnace as a heat source. I bought three for $10 at a
country auction- lots of spares. You will have the blower/fuel pump
situation already worked out and the fuel is more compact and easier to
handle than propane. If you are pouring a substantial keel (mine was a
traditional-shaped 4200 pounder) it might be worthwhile to have a
melter welded up from steel plate. Then you can incorporate legs, etc
in the design. One of the early WoodenBoat mags had some details.
You might also want to have an oxy-acetylene torch on hand to preheat
the various spouts and pipe to make sure you don't get lead freezing
enroute to your mold.

Best to keep the whole operation quiet as the neighbours are apt to get
upset and blame their kid's defects on your lead project!

John