How can I, if possible, repair a three inch gash in the sidewall of a tire. Tire shops say they can't repair it, and it's a discontinued tire, so I'd have to buy four new tires. Tires have great tread left on them so I need a fix for them. They are not road tires, just used for off-roading.
Any advice is appreciated.  

some sidewall damage can be sectioned from the inside if the damage didn't penetrate.

what tire and size are they?  

BFG's AT 325/60R15's....a discontinued model. Plenty of tread left on them, but the gash goes all the way through the sidewall. In other words, if I can't fix it I'm stuck with three good tires and one paperweight. I'd have to scrap all four tires and that's a waste since they have great tread still on them.  

yep, but i'm sure some can be located  

Ohhh, that sucks. Start calling mail-order tire compaines. They may have a couple. Try Summit Racing, Jegs,...  

if all else fails, buy two similar tires in the same size and put em on. just rotate them front and rear instead of criss crossing them. the plus side is that you'll end up with a good spare too!  

I am sorry to hear it went all the way thru.  I have been nursing sidewall slashes and cuts for years using 3M Weather stripping cement, Shoe Goo and other various cements.  For a write up and pics, check out:  http://www.savagesun4x4.com/enter/how_to_stuff/sidewall_repair_for_tires.html  

We got a nasty sidewall gash on my friends XJ down in Baja a couple years ago, the spares we had were smaller so we just plugged the sidewall.. it held for a good 300 miles, just enough to get us back over the border...

Anyway, yea, that tire is done. Sidewall hits suck...  

could you put a tube inside for added 'inflation'security?  

I think you could if the cut had a section patch inside to keep the tube in...I don't think I'd be driving it on the hwy though..