Tallest wheel on a 72 swinger

I guess I'm not even sure what the goal might be for taller tires. Lowering the final drive ratio? Extra ground clearance? Longer contact patch? More ride comfort? Style?

Almost any of the above can be accomplished in different/better ways.

First off, the diameter wheel you use doesn't change anything in tire height.

26 is safe in the stock location. You can easily run more, certainly up to 28" without issue, by simply spacing the front shackle back.

Last, please run the 15's. totally worth the money. 14's are outdated in both looks and size as well as tire availability.

Agreed on all counts...well mostly. The 15s are also way outdated in terms of looks and tire availability! :D