I have to admit, I HAVE done the two rear springs thing in the past. Wind a pair of SHORTENED ones together, weld at the ends (and, I think we were securing to the spring seats as well). It is not an "insanely high" spring rate, but adequate. However, you DO need a lot more shock absorber damping to handle them. Seems a lot simpler today when you can buy this stuff for peanunts just to spring (sorry for the pun) for a used set on the 'tex or something.