I just went to the garage and got out my tap and die set and the 3/8's fine thread was spinning onto the bolt perfectly and not loose. This was one of the 4 bolts on the TC if that helps you any.
Some places have dual bolt circle converters.
I'm pretty sure the Marks are the smaller ~10.65", not the ~11.5"...
those aint the bolts i was speaking of, but thanks that will save me some time when i get the car on the lift.