Pre-fabbed wheel tubs...........what size?

[Pontiac signman]

Guys,

Can anyone help me decide on which tub length to puchase?.......stock '67 A-body tubs are 34.5", pre-fabbed one's are 36, 38, and 40". If anyone's done this and can offer some advise before I get too far in.....I'm all ears.

I have the quarter window (side back window) tracking to deal with also, but want to fit an 18"-20" rim in the back.

Here's link to my project to show ideas and what I have..... https://www.pro-touring.com/showthre...-me-and-my-car............

Thanks