I would not feel comfortable riding on springs that have been altered from stock shape after all those years; unless the heating and recurving is done right you could end up with brittle springs. It is much easier to remove a leaf or two if you want a slightly lower and softer ride. Remember to disconnect the steering linkage before altering the ride height so you don't bind/break anything.
Here is a page that describes the procedure on a TaskForce. How far you can drop will be limited by the rubber spring snubber on the frame, so take some measurements; you may want to buy monoleafs after all.
