I've torqued a bunch of 7/16" NASCAR connecting rod bolts to over 100 ft/lbs., but they're a bit better alloy than Grade 8. I'd recommend 65-70, with a drop or two of red Loctite to make sure they don't vibrate loose. Good luck!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!