1st, Get the transmission redone. (Assuming it's an Auto, Fill in your Signature Block. It's under "User Control Panel" tab) You did not say how many miles you have on the truck, so if it's low mileage and the trans is in good shape, then a Valvebody and Torque Converter should do it. It the transmission is worn out, then go the full route. It seems the 1st thing to wear out, Not break, is the 2nd gear band. It went on my truck, then when I went to the transmission guy he had one in the shop with the same thing. It's an expansive Mod, but Necessary, A good VB and TC just feels right, Firm, Quick Shifts, and a smooth TC Lock Up with a very small RPM drop as she locks up. Oo.
The next step transmission Mods or not is an After market Lift Pump, and a Fuel Pressure Gage if you don't have one. Never let the FP get under 6 PSI if you can, as that will kill the VP44 (Injection Pump). After that, do a low restriction exhaust system, sounds like you have plans for that, make sure it's at least 4" Turbo back. Do an Intake, BHAF is a good place to start. A BHAF is a Airfliter element out of a Big Rig (look here for part Numbers:
https://www.turbodieselregister.com...ion-1998-5-2002/184086-bhaf-part-numbers.html ), Just take out your stock aircleaner box, and then put in the BHAF attaching it to the Intake hose with the factory clamp. Now would be a good time to remove the Silencer Ring, for that big Turbo sound :-laf To do that remove the black snap ring around the Turbo inlet and then the ring just falls out. Search on Silencer Ring.
After that then the big bucks start to flow! To make power you need Fuel and Air. To get the fuel, You need to do Injectors, and or a "Fueling Box". To keep the EGTs in check you need change the Turbo (Air) to one that matches the injectors. The Combinations of the above three are limitless

I know of a lot of guys who have had good power (450 HP+) with Mach 3 or 4 Injectors, II 62/12 SPS Turbo, Smarty(Downloader:
www.smartypower.com ), and
Blue Chip FMS. (Fuel Management System)
Diesel Performance Specialists, VP44, 47RH, 47RE, Cummins Diesel Performance
Now that I have the transmission and support gear, I guess that I'll wait till some more money comes my way. "Speed is only a question of money, How fast do you want to go, How much money do you have to spend?" Just remember, You can easily have 500 + HP, that you can drive on the street, loaded down with whatever cargo you can fit, with the AC cranked! Try that with a Big Block Gasser!

Enjoy, Moose