68 Camaro, wheel backspace(DSE quadralink n subframe)

[qwkswede]

Hello,
I'm moving along on my 68 Camaro convertible project. I want to get some wheels ordered in the next couple weeks. I'm looking for some recommendations for width and backspacing. I'm sure this is a question that gets asked every other day. So if there is a recommended way to get measurements easily to fit big tires on these cars, please lend some advice.

Here are my guidelines.
The front suspension has the DSE narrow subframe, with the C6 vette uprights. An 18" wheel is the min. diameter here.
The rear is DSE quadralink setup with coilovers. and the DSE minitub kit. The 9" rear axle measures 56.5" wide from mounting flange to mounting flange with the brake rotors mounted. I'd like to run an 18" wheel in the rear also.

From poking around here, it looks like I can run 335mm rear, and 275mm front tires. And keep the diameter of the tires at about 25-26", close to the stock diameter.

Can I squeeze anything wider in the front? 295?
Is anyone running the above widths on a '68 with similar chassis/body mods. What backspace am I looking at for this setup front and rear.

Here are some pictures of the rear wheel wells, I thought they might help. You can see the frame notch for the minitub job.