Ahh Dizzy, we meet again....but on a different post....
My advice would be to buy the style of rim you prefer as new items......that way you have the correct back space, offset, and center bore measurements suited.
Ride height and stance, and of course wheel/rim choice can make or break the look.
Once you come up with wheel/rim/tyre choice, you can work on getting the car to sit correctly with your lowering plan.
I am going with 15 x 8 Superlites all around and fitting them has it's challenges, but is not impossible.
Aussie Phil has a great looking stance on his 68 and I recall he has gone to 17's, So I am sure he can have some advice.