I just went out and measured my car for you to use for reference if needed. Mines a 65 with 73,000 original miles, no slop in the hinges and has never been in an accident of any kind.

Front door to fender measures and average of 7/32"

B pillar between the windows measures 1/16" (yes, pretty tight, but factory)

B pillar at the top corner under the brightwork is super tight. Probably a business card and a half at best.

Rear of the door to the quarter measures about 3/16". It varies a bit top to bottom due to the curve of the opening, but not much.

I'm not sure how dedicated you are to fixing the problem properly, but if the door can not be adjusted enough to yeild satisfactory results and you don't want to spend the money to have the quarter panel and rocker cut apart in order to remedy what sounds like shoddy bodywork, you could have the edge of the door ground down in the tight spots and have material added in the wide spots. This is very common practice in the hot rod and custom world. Early american cars left a lot to be desired in the fit catagory. Many times the only way to remedy excessive or overly tight gaps is to do as described. It would render the door dedicated solely to that vehicle, but it would be a whole lot cheaper than having the quarter and rocker cut apart and rewelded. Just something to think about I guess.

Chris