Your getting there! I would still keep the rear torsion bars in there and go with a lower spring rate in your helper. You only have to reindex the bars once for your desired ride height and then that's it for a street car, you never have to touch it again.
I would stick to stock Euro ride height which I think is about 1in lower than US. Just make sure your front control arms are parallel to the ground and if there any rake, that the back is higher (1/4-1/2) inch higher than the front, but level is good.
You don't need to match the spring effective exactly right front to rear, just close enough. You can dial in the handling to your preference once you drive it a while on your new suspension using bigger/smaller sways and tire widths. It's a process and everyone will like things a little differently.
Finally, if you do remove the torsion bars make sure you remove the rubber "doughnuts" on the spring plates and fit something like Delrin. You will also need a good alignment after everything is fitted. Lowering will push your tires into positive camber territory and you don't want that. GL
Here's some other reading:
Suspension