The only real issue I see with a 5.9 6BT is the weight of the engine.
If you start looking for one....
If you go the VP-44 injection route, don't get a 53 block number, they tend to crack the water jackets.
If you go with a P-pump 12 Valve..... look for an IH block (yes International Harvester) they are the beefiest of all the 6bt blocks, and the most sought after, for re-sale.
I'm guessing you don't even want to venture into the CR (common rail) territory for cost alone.
the VE-pump (1st gens) some came with intercoolers, some not, I don't remember the crossover point... you want an intercooler.
Auto trans, came out with an HY-35 turbo some years..... much smaller exhaust housing. you want an HX-35..... and I would suggest a cheap easy mod... 250 dollars or so to convert your HX 35 into an HX 35/40 for spooling purposes, and to avoid the shaft snap common in a straight 40/40 turbo.
A cummins will cost much less to mod than any PS, and yield more gains....
mainly because of the cost with injectors, and turbo's.
I had mine head-studded, O-ringed, spraying water/meth, Industrial Injection 66/71 turbo, tst fuel, edge timing, 200hp 7hole .010's injectors, ats exhaust manifold, BHAF intake, 1/2 fuel lines, 150gph Airdog on a toggle switch,
I also had to run a South Bend Dual Disk clutch.... could launch in 3rd at 45psi with no slippage after dumping.
billert input shaft was a must.
NV-4500 will be your cheapest trans route with the manual.
You will need a sled pulling clutch dual or triple disk if you take the NV-4500 or 56 (6speed) route.
so what are you looking into?
i just know a little about certain topics.
Frank