1969 dart wheel and tire size?

Interesting topic as I"m doing steelies this week for my 69 Swinger.
This thread is relative to the rear only...
Car has aftermarket axles[5x4.50]and drum brakes.
Cal Trac leaf springs and shocks-car does sit low on the rear..1/4 panel just above rim height.
Currently riding on 15x7 Welds with 4.50 B.S.235/60/15 MT Drag radial
I tried factory 15x7 Chrysler steel wheels w 4.25 bs and I couldnt get a tire small enough to clear the 1/4 panels[street side]??
I could get a 235 in there,drop the jack done but NO WAY would I drive it like that....waaayy to close.Yet I had lots of clearance toward the leafs??
So I getting my centers rewelded to 4.75-5"back spacing to to hopefully fit a 245/60/15.
I guess at the end of the day,every car can be a bit different and the cars are so old that things change over the years....rear ends,axles,leaf springs and hangers,ride height,1/4 panels etc.....even tire manufacturers vary...
So there"s no 1 answer to what fits..IMO