Rn, I got your message. I don't know what's up with the pdf on the frameplans. I'll look into it.
Here's some things to concider;
~ build a Model A type frame, easier to mount your fenders and gives you more room for exhaust, battery, etc.
~ the running board aprons will be sandwiched between the body and the frame, filling any gap between the body and the frame.
~ the pickup or coupe rear are wider than the sedan fenders, should fill the gap from the narrower body.
~ using a dropped I beam axle with the spring over the axle will keep a stock type of appearence that your pic shows
This is a doable project. Total sold a '27 body with '29 fenders and IMO those fenders looked great.
Widening the body, again IMO, will destroy the look of the car. The stock body has great proportions. I would leave it as molded and make the fender assembly fit the body.
Oh, buy the way, welcome to the site!!!!
Ron