Stock Body - conflicting tire sizes

[g356gear]

Hey guys,
I have a stock body 69 BB coupe that I am looking at giving a more aggressive stance. I am looking at the DSE Speed kit 1 (2" drop+ 18" rims) in the front and a Leaf spring (3" drop+ 20" rims) rear on the car. I don't want to cut up the body or subframe at all, so that is my reasoning for going this direction. My problem is some different information I have gotten on what rim size will fit the stock body with the lowered suspension mods.

DSE and Fikse say you can go 8" front and 9.5" rears maximum width. I have talked to other wheel manufacturers who say that on their project cars they have only been able to run 7" front and 8.5" rears without rub issues on the fender edges.

Any feedback would be appreciated.