:lurking:
Next we need a chart to convert those old tire sizes into modern tire sizes.
here is another one.....
Converting old tire sizes to new sizes...
This one Alan?
https://www.tacomaworld.com/tirecalc
I found this interactive tire size calculator very useful as well.
https://tiresize.com/comparison/
Chart for Polyglas GT tire diameter to determine your speedo gear tooth count.