Dude, you have an '89 model. Swapping in a 4.0 is easy and would yield better results if you still want to turbo later.
No replacement for displacement and all that.
Plus the 4.0 makes gobs of torque. It turns my 33s effortlessly (3.73 gears) whereas my 2.9 struggled on any hill.
If you ponder the 4.0, shoot me a PM and I'll send you the wiring document I used for my swap.
And seriously think abut the following points:
2.9 hasn't been built in a LONG time. Parts = getting more scarce and more $$$
2.9 has weak heads. Add FI and ???
The junkyards are FULL of good 4.0s in front of blown A4LDs
If your truck is manual, you're going to need a 4.0 clutch setup either way you go. The 2.9 clutch is a steaming pile behind a 2.9. Add horses and watch it slip. If you have A4LD, that's a whole 'nother can of worms.
Not trying to dissuade you from FI the 2.9 (well, maybe a little

), but be sure to fully explore your options before spending dollar 1. Find someone who has done what you are planning if possible. Nothing worse than dumping loads of $$$ and time into a project that leaves you unsatisfied when you get the final result.
All that said, I've personally seen a 2.9 with a Paxton centrifugal on it sitting in the 4 Wheel Parts store garage. The owner wasn't there so I couldn't ask his own experiences with it, but it obviously CAN be done.
HERE is a video of a turbo'ed 2.9 in a Ford Sierra. Looks like fun!
I'll see if I can find any info on that Paxton kit and edit this if I do.
Good Luck in whichever way you choose!