49 to 54 chevy extended cab

I am looking for some pics of a extended cabs on a AD truck.
How much can they be extended and still be in proportion?

 

I was thinking of a 4 door. I have 2 kids now 2 more door would help.
Bill

 

go to some of the railroad sites in cold areas. they built AD snow removal machines with different cab configurations. actually did see one years ago and thought it was some homemade unit but turns out it wasn't.

 

I extended the one in my avatra 10 1/2 inches to fit my shorter utility boxes
have a cut by cut on my web site under shop truck build

www.oldcarglassguy.com

and another that looks good extended the doors about 6 inches