My '73 Dart experiences a 'snap' oversteer on wet road cornering.

- Setup-front:
1" Torsionbars
Hellwig front swaybar
Poly-bushings everywhere, 'cept UCA's (Moog offset).

- Setup Rear:
7-blade leafsprings
Poly-bushings
NO swaybar

318ci / stock cam - A518 trans.
Auburn SureGrip 8-3/4" rearaxle with 3.55 gears

Two propane tanks in the trunk (1 in spare tire well and 1 under package tray).

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Even at moderate/slowish speeds I feel the backend wants to break-away / come around the moment I slightly get on the throttle.

Front swaybar has it's Hellwig swaybar struts.
Plan to replace these with Viper end links, hoping this will make the swaybar do its job better.

Also, if that doesn't help, I'm thinking I either need to increase the torsion bars diameter, or maybe take out a blade in the rear springs?

The latter is cheap, but feels like a big 'step backwards', and the car needs the support at the rear for the propane tanks.
Upping the torsionbar diameter is not cheap, but will this cure the oversteer?