Diesel Bombers - 1st Gen. LOVER!

Unfortunately I have waited until last year to obtain one of these workhorses. I fell in love with them back in 89' when I first saw one with the cummins installed. Unfortunately I now am disabled and have an anorexic income to use with my truck. My baby is a 92' Dodge W-250 ext. cab. 4x4 LE package with 150,000 on a 12 valve I/C turbo. Unfortunately I have one weak link in it has the much hated A-518 auto trans. I would like to install a NV 5-or 6 Speed later. I have taken care of the K.D.P. problem, serviced and changed all fluids and filters. I installed a B.D. fuel pin, 3200 Rpm. Gov. spring, Torqued all head bolts, Gave it a K&N filter in the stock air box. I have primed and painted the roof and hood of the truck since the paint was faded into major surface rust. I am having trouble locating a water leak inside the floor on the passenger side. My Heater core is o.k. But I do have drips from the vent on pass. side occasionally. I also have this wicked shake in my front steering from 35-40 mph. unless I full throttle it past that speed. I just love this truck. I want to put a fass Air Dog fuel system on it, and a 4"turbo back exhaust system. I want this truck to really breathe, and pull when towing. Yet I don't want to hurt my current 20-21 MPG. rating avg. I am getting right now. I want to also show up my friend who has a 2002 F-250 6-Speed 7.3Turbo diesel with a three stage programmer. He is just a little too cocky!