A six and a half with REASONABLE power levels will do fine with TTY bolts.

Try shoving big boost and a buttload of fuel into a 6-1/2 and it will suffer....

I tried a set of MLS gaskets on a 6.5.....NOT ENOUGH HEAD BOLTS IF USING TTY..

ARP studs may have worked better.......

The factory stuff is always right on the ragged edge.....You always need more when you plan on flogging it hard.....