I have messed with scales a lot however everything has been for dirt car applications...

When moving cross weight (opposite corners) you need to be able to adjust in and out on all 4 corners to get the full effect.

I fully understand how this isn't always possible with leafs and torsion bars...Torsion bars will move weight just as you would like but have no adjust-ability as far as the rate...(spring rate)

If you were to use a longer shackle on the RR you would add weight there while also pushing the LF back down and leveling the ride height back out...A 1/2" lowering block on the LR may also do what your looking for as it will transfer weight onto the RR while lightening the RF.

There's a way to get nearly any number you want without sacrificing ride height but you'll have to be willing to experiment a little.

Ultimately what your car likes best will determine the direction you'll need to take...