Its easy enough to measure the torsion bar diameter. You can use a crude caliper - like a c-clamp if you don't have a real one.
Wallowing - my first suspect would be shocks. Check each corner.
That's where I'm going with this. Go find the problem. Whether its bushings or shocks. Also check the rear leaf springs. They have bushings too - and they control the rear lateral motion.
If you do find the car was set up with a slant six suspension, (t-bars and leafs) then converting to the ones used on v-8 Darts is a good idea.
If you are looking to reduce body roll in corners ( a little different than 'wallowing' but your may mean it different than I take it) then the front anti-sway bar is a good addition. However to put a factory bar on will require welding tabs onto the lower control or getting a pair made that way. You can get aftermarket bars - such as from Firmfeel, that will not require welding. They will be larger than stock, so if going that route, discuss with them the matching package (t-bars and rear leafs).
