Buddy of mine owns Discount Muffler in Piperton,Tn and he is familiar with diesels.
I dont know what all he does, but he did my gear swap for DPC and a few other things.
Not sure on the spring perch relocation, as Im not familiar with what it entails.
Give him a shout. Eddie 901-853-1767
If you need something done cab-off, closest reputable shop would be Swamps.