They are
torque thrust D's.
I have these on my 68 as well with the same 15" x 7" footprint but running 255/60 rears and 225/60 fronts if memory serves me correct. I'm getting old and my memory isn't what it once was. Might be off a touch on front tire sizes and too lazy to walk out to the shop to confirm as I'm enjoying my coffee right now.
Just an FYI on Polyglass sizes. E60's are 7.50 tread width while F60's are 8.25 wide. The G60's are only 8.40 so not much wider than the F series. The L60 is 9.00 wide but they are also an inch taller at 27.99 so they won't fit the fronts.