Chris
I know it has been done before, I have seen pics of the conversions. One used a seperate gear motor that hung beside the regular motor and the belt switched back and forth between the two motors.
A set up of pulleys would work almost. the import bandsaws used four step motor and countershaft pulleys. this gets the speed down for non ferrous metals but is still too high for steel. A 3 ph motor with a VFD drive would help in conjunction with the pulleys or gear box.
Delta used a gearbox built into the lower housing and a series of belts to step between either the gear box, or direct to the lower pulley.
The wood bandsaw is usually running about 3000 SFPM, and for steel you are aiming at about 100 SFPM My Delta is from 35 to 335 in six steps plus the 3000 for wood.
Posts some pics of how you have done this on yours.
Walter