Ok I talked to Nick at Thorley's and he said that since I have a classic GMC their 310Y-49 LT Tri-y headers will fit on my 6.0. But I have to cut back my cats. My question is, will Dynatech's y pipe connect to these headers?

 

no thorley's are a midlength header.....just have an exhaust shop make you one

 

Have the muffler shop make you a y-pipe. Mine cost about 75 bucks at the local shop here.

 

I dont think you have a Y pipe. At least i dont on my 06 vortec max

 

The Thorley Headers should come with 2 adapter for your cats. At least when I bought them 5 years ago it was included. You cut your exhaust pipe just in front of the cats, weld on the connector and then bolt it to the header. Remember, measure twice--cut once.