Snapped bolt in crankshaft installing harmonic balancer

[blubuckaroo]

I'm not trying to hijack this thread but I was researching this harmonic balancer bolt and found that in my Chilton's manual it lists two different torque specs.
'66 to '73 ... 70-90 ft. lbs.
'74 to '77 ... 35- 50 ft. lbs.
Is it a different thread pitch or crankshaft material? Maybe a misprint?
Chilton's is the only place I could find this different torque.
I ran into this when assembling my motor and forgot to ask the forum why the difference?

 

[DJs74]

I'm not trying to hijack this thread but I was researching this harmonic balancer bolt and found that in my Chilton's manual it lists two different torque specs.
'66 to '73 ... 70-90 ft. lbs.
'74 to '77 ... 35- 50 ft. lbs.
Is it a different thread pitch or crankshaft material? Maybe a misprint?
Chilton's is the only place I could find this different torque.
I ran into this when assembling my motor and forgot to ask the forum why the difference?

According to Tom Monroe (HP Books) / Small Block Ford Engines: the harmonic balancer torque is 70 - 80 ft. lbs.

DJs74

 

[hboutlaw]

Update: I took the bronco to my mechanic that I use for my other cars. They were able to successfully remove the rest of the bolt by drilling it out (small bit all the way up to a bit just before hitting the threads) then using an easy out. They will clean up the threads then use a slightly longer bolt. I already had the radiator out but they removed the front grill for better access.
Thank you all for your comments, suggestions and advice.