Are we talking about an A-body convertible here?

Mopars (any Mopar) needs frame connectors. Convertibles need all the body-strength they can get.

Larger T-bars can prevent bottoming out/too far on dips and speedbumps, especially if you like a lower stance on the car.

Shocks can make or break a car's "pleasure to drive".
Cheap shocks usually can cause a rough/hard ride with upgraded springs.
Your short sidewall 18" tires won't smooth out the car's ride either.

Because shocks need to match and work with the torsion bars, I wouldn't go too big on the bars for it being mostly a cruiser car.

I've got Just Suspension 1" bars on my dailydriven '73 Dart, but they don't reproduce these anymore.
I recall PST has the 1.03" bars and FirmFeel carries the 1.06" bars.