Which Torsion Bar?

Hi guys,

I have a 400 big block in my 68 dart which was a drag race car, I'm trying to adapt the car to roads here in the UK.

I am thinking of getting a set of QA shocks and some Torsion bars which are uprated from standard.

Can you advise what Torsion size I should be looking at considering the big lump of metal up front in the engine bay.
The car is mini tubbed with 295/60/15 tyres on the rear, 185/55/15 on the front.

At the moment it corners like a ferry, I've not looked at what size torsion bars are on the car.

Thanks,

Jon