It is still going to have a ton of body roll with a transverse spring, without some sort of sway bar you are going to be putting a lot of stress on the shocks.

Whenever I want to convert to open driveline from a closed, I just ordered the conversion from Speedway Motors, I'm sure they still handle them...

I have a set of Speedway's urethene busings in stainless rod ends that will be going into a triangulated 4 link under a Camaro.

Your radius rod/torque rod idea should work, but I would really recomend a sway bar. Those old hi arch (or low arch) transverse springs are not near as stable as one would think.... Been there, done that on a '29..... Had everything done and painted, THEN went back and added the sway bar.....