Not sure if you got them already, but
go to Fastenal!!!!!! Here's their website, you should have one close to you somewhere,
http://www.fastenal.com/ I guarantee you that they will have them.

If I remember correctly, they are 7/16-20, and you'll have to determine your own length. I wouldn't use stainless for the drive line. Stainless is softer than grade 8 bolts, and you don't want to risk shearing any of those bolts off, so just get some black oxide grade 8 bolts, and never have to worry about it again.