Originally Posted by Ken_Shea RBinAR -
The strength of a bolt may rely more on the material then the thread, I.E. soft no carbon steel=weak bolt, fine threads do however offer more holding strength. I am sure there are specs for this but I am not sure where. Do a search and see if anything comes up.
Well that was easy 
http://dodgeram.org/tech/specs/bolts..._strength.html |
Thank you so much for the reference that's exactly what I needed. What I needed was a thread strength to hold 9000 lbs. load with some margin for error. Acording to the site any good grade 1/2 X 20 bolt with sufficient length threads will handle that.