In all the searching I did previously on what all had been done to this truck. I think I had found that the PO had given that transfer pump adjustment about a 1/4 turn, I also found a post where he wished he had left that adjustment alone! IDK if he tried to put it back.
Maybe...
My 95 is set at -0,70 or somesuch and does fine. iirc GM spec is -0.45 to -0.75 but you can go as far as -1.94 without setting the SES light. I honestly don't know what that gives you, but supposedly better "off the line" performance and louder clatter. I personally prefer not so loud...
get you some fuel jugs or a clean barrel, if you can rig up an inline pump and a battery to empty the tank in to the barrel or fuel jugs that way. heck even some clean 5 gallon buckets with lids will work. when done, you can use that same inline pump to put the fuel back into the tank.
that...
also if your wanting to keep your odo showing original mileage, I don't thing it's that hard to pull the speedo apart and swap the number thingy or the whole speedo gauge in the cluster.
that should plug right in to the existing harness. not sure what the bottom left gauge is for, I assume factory boost?
if the tach doesn't work, then we'd have to see which pin in the harness goes to that gauge, see if there is a wire in the plug, trace it back to the engine compartment or add...
most Napa's or a local farm equipment parts places should have that hose in stock. again you'd probably need to see and look at the numbers on the hose to be sure, but your chances are better at those places.
I did mess with it some and moved the IP back to where my blue paint line lined up with each other. when I was messing with it I first tried to push in the advance piston on the lever. it went to missing and belching whitish grey smoke if I tried to move the IP to the passenger side more...
just a thought. you can find other squarebody trucks with the tach option. pull that tach and swap it for your fuel gauge. then swap the low coolant light for the fuel gauge. you might need to calibrate them but then you'd have factory gauges in there and retain the unmolested factory look...
I recall seeing some pics of your setup and it looked very different than others that have them. would you mind posting some more pics that details how the turbo setup is?
you've got you a highway cruiser with that setup, but don't expect to pull anything heavy. being that you have a 4x4 if you decide to do a gear swap, youll need to do both axles. but if you want more power to climb and to pull/haul go for 4.10's or a higher ratio then install a gearvendors...
I'm not familiar with the ATS turbo, others here are. I will let them chime in on that for regulating boost pressures. just keep it under 12psi unless you have head studs installed. but also to avoid cracked main webs.