easyrider,
I am runnin 18 x 8" up front with 225-40-18 yokahama s-drives
I have got 20 x 9.5" on the rear with 285-30-20 s-drives.
That is as big as you can get on the rear without tubs. Hope that helps !!
The build looks GREAT!! I have had my 68 pro touring done for a couple years and wish I had joined the forum sooner to get pointers during my project. GOOD LUCK !!