With the parameters you set down - no modern stuff, gasser style, etc., and that you have a blank cnvas to work with. I don't understand the parallel leaf spring/torsion bar setup you mentioned. Seems it is an 'either/or' rather than an 'and' for those two systems.
Is the frame in good shape?
I have some ideas of the direction I would go. First, you can get a custom tube axle made to the right width, drop, king pin bosses, etc., so that is no problem. I would have a custom tube axle with a Ford type cross spring and 4-bar links rather than parallel leaf springs. First it will save a pound or two. More importantly, it will eliminate bump steer that is unavoidable with parallel springs. Chuck Finders was a famous gasser chassis builder in the '60s and he went to this setup from stock parallel springs on Willys cars. Look at pictures of his Altizer, Finders, Kibler Traveler '33 Willys A/GS car for a great example of it. With it you can use parallel or cross steering and have a very stable, no bump steer system.