Wheel well sizing request

[march11934]

Hello everyone. This is my first post in this forum. I have really enjoyed reading and learning from this posts in this forum, however I can't seem to find any info on wheel well specs. I have a 70 Cuda that I intend on building up to pro touring. I am currently working on the back half of the car. I have been collecting tire info from various posts on this forum and 18 inch rims seem to be the most popular. Looks like a 305 to a 335 width is the tire of choice. I'll probably be going with a 45 for a little sidewall height.
That said I need your feedback on what wheel well specs your running to fit a 12'ish in wide tire?

An e-body rear frame rail runs in a splayed layout. I don't know why... so it starts narrow at the front and works out wide as they progress to the rear bumper. This causes a bit of a problem when measuring out for "potential" growth if widening the wheel wells, which I intend to do. Without touching the frame rails I can get just about 14 inches wide stretching to the rear portion of the frame rail. There would be more room to go it they were more parallel. This should fit a 335 but I don't actually have a set to mock up. Thought about buying a burned up set from a junk yard...

I have considered removing the rails and shifting them more parallel but not sure it's worth getting into if the wells don't need to be wider than 14 inches in the first place.

Any specs on wheel well sizes for a 335 tire would be great feedback.
Regards.
march11934