i use a Hancook or Kumho 185/80R15 on my 68 Satellite . I have also fitted these on an Aust Valiant - similar/same as a 67-69 Dart Neither have had clearance issues . I use a 4" rim the Valiant a 6" rim
Tex
I was just looking at that size on Summitracing.com. Coker 57986 has a red line that might be removable? It's 27 tall, 7.28 section, 4.75 tread. $178 each.
My M/T Sportsman is 26 tall, 6.3 section, and 4.8 tread.