Maybe the belt isn't lining up"square".

Is it a home-made alternator conversion?  Trackalongnamex is probably on the money with the belt not lining up. 

Its a trail tough bracket and it is lining up perfectly.

How are you determining the pulley's are lined up? Have you checked the pulley's ( all of 'em) surface and edges for any nicks or irregularities that could chew up the belt?
Have you checked to see if the Alt bearing is spinning smoothly? Maybe it seizes and spits the belt after running for a bit. The belt may be a symptom, but the belt may not be the cause of the problem. Maybe something in your truck is causing a big amp draw and causing the alt to slow or lock up? Maybe your kid just likes to bang redline and the belt just flings it's poor self off in an act of mechanical suicide ! That problem's easy to fix.

I'm using a belt hog to check alignment, and the pulleys are all spot less.  I'm not an idiot, I'm a master auto tech.  I was just hoping someone else may have had the same problem, the new alternator pulley is just a little narrower than the samurai pulleys and I think it is causing the problem.  I am going to replace it and see what happens, it's just a little weird that there are no problems the first time I drive it and on a long drive and then a short little drive later and the belt dies.

Thanks for the response
 

Your right in that it is weird that your throwing belts like that.  Most of the Sammy's in our club are running GM one wire alternators without issues. 

I had trouble with mine wobbling after a while and tearing up belts, but it took 6 months of driving. We beefed up the bracket and no more problems!

So when I pulled everything apart and check stuff out I found that the pulley on the alternator is a little narrow and the belt is riding high.  I hope I can make the stock pulley fit it and line up good.

I went to put the stock pulley on the alternator and the hole was to small, I looked around and found a few old gm alternators and found an old 10si and the pulley looked right.  I had to throw it on the lathe and thin the hub down a1/8" so I could fit a lock washer on it.  I ran it 20 miles around and went and tried out the new my side 2 I threw on it and tried some steep climbs for fun, the belt is still there.

Looks like the pulley was the culprit

Hey buddy, hope you didn't take offense, I certainly didn't mean to imply you were an " idiot." That was never the intention. In any case glad you got it figured out, turned out to be a pully issue after all.
I run a Gm alt on my Tracker with a trailtough bottom bracket. Differrence is Trackicks use ribbed type belts, and the GM alt I got had a proper pulley, just a 4 rib instead of a 3, but the belt lined up in the inner 3 ribs of the pully just fine. It's still working well 30k later.

No offense taken,  I'm just a little currious as to why someone like Brent would go through the hastle of building and selling an alternator bracket and not throw some good basic info out like suggestions on fittment and belt length.  Trail tough makes some good products and I have bought stuff from them for years, just a little disappointed in this. 

Maybe I will get a list together and post it up
 

I guess he figures we need to do some of the work at least! As far as the belt length goes, wouldn't that depend on the style and size of the GM alt your using? I'm uning a 105 amp gm alt, and it came with a pretty small pully compared to the stock Trackick pully. Maybe each different gm alt has different size pully, hense different size belts would be needed.

Brent also sells a darn good disc brake conversion - again, with no instructions. Maybe that way a "disclaimer" is unnecessary.

saw this, hope it helps
http://www.zuwharrie.com/gallery/thu...php?album=1368