Ok, lets be real here... twin turbos on a 3.9? I am not tryin to be a jerk, but you are pushing rope dude. (and look at my sig, I own a turbo V6 car so I like this in theory actually)
Why twins? Ever noticed most twin turbo cars are faster w/ singles?
The reality is your truck w/ a 12v Cummins w/ $1,000 in mods would do more, and wouldn't be as much money in custom parts, or hard to fix because only a few know what it is. It'd be fast, have MORE torque and much longer reliability. With 200K on yours, I'd strongly consider doing diesel, or selling and buying the same truck in diesel. Putting $5k in a $5k truck is hard to do in the end.
Regardless of what you do good luck, I dont wanna pi$$ in your cheerios, but after building cars/trucks for over 20 years,and helping turbo everything from 240s, mustangs, camaros to full size broncos I have learned that you can spend a ton of money making it work to run 2 secs slower than you anticipated.
Seriously consider diesel.
12 Ram express QC, belltech 963sp and McGaughys spindles, debadged,Polk audio, smoked lights, tint, bedcover, and lots more
06 Stratos 201 Pro XL 225 Yamaha