Need help with size, thinking 18's on a 68 dart
I'd run these...
Summit Leged S's. I run the 17" version on my Challenger. The nice thing about them is the hub bore is large enough that they fit the stock rotors without any issues, unlike most Ford rims.
18x18.5 with a 5.5" backspace for the front
http://www.summitracing.com/parts/sum-142-8865gm20/overview/
18x8.5 with a 4.5" backspace for the back
http://www.summitracing.com/parts/sum-142-8865gm6/overview/
The problem with stock spring location A bodies is that you can't run the same backspace front and rear. If you wanted to rotate wheels, you'd have to buy 4 of the 18x8.5 with a 5.5" backspace and use a 1" spacer/adaptor out back. I've run those type of spacers before (they bolt to the lug studs and then have their own set of studs) without any problems, so you could do it either way.
As far as the same size tire all around, 245/40/18 would be the safe bet. But a 255/40/18 should fit as well, although on some cars you might need to trim or roll the rear quarter lip a little bit.
I'd run these...
Summit Leged S's. I run the 17" version on my Challenger. The nice thing about them is the hub bore is large enough that they fit the stock rotors without any issues, unlike most Ford rims.
18x18.5 with a 5.5" backspace for the front
http://www.summitracing.com/parts/sum-142-8865gm20/overview/
18x8.5 with a 4.5" backspace for the back
http://www.summitracing.com/parts/sum-142-8865gm6/overview/
The problem with stock spring location A bodies is that you can't run the same backspace front and rear. If you wanted to rotate wheels, you'd have to buy 4 of the 18x8.5 with a 5.5" backspace and use a 1" spacer/adaptor out back. I've run those type of spacers before (they bolt to the lug studs and then have their own set of studs) without any problems, so you could do it either way.
As far as the same size tire all around, 245/40/18 would be the safe bet. But a 255/40/18 should fit as well, although on some cars you might need to trim or roll the rear quarter lip a little bit.
