Driveline Vibration Specialist

Hello everyone. I have an '86 Pete 359 with Spicers 6x4. I'm experiencing a nasty vibration starting at about 45-50mph and gets worse the faster I go. I've checked everything..and I mean everything. And most parts are new (it was recently restored). What I need is recommendations in the NJ, PA, NY, DE region where I can take this truck to a driveline specialist who can drive this truck and figure it out. A shop with drive shaft balancing capabilities etc. Someone with knowledge of old trucks and transmissions and who can actually drive and shift one. Any suggestions would be greatly appreciated. I have a close friend who would be able to figure this out in about 10 minutes but he is so sick from chemo that he's too weak to even climb up in the truck. So I really need some suggestions. It is a constant vibration..does not go away when you let off the fuel or place in neutral. God Bless and thank you!