Running any vehicle on a dyno is just one way of checking &/or testing the results of whatever tuning work has been done, it's not actually 'tuning' per se!! (they used to be called 'rolling roads' & are effectively used to control & measure the 'road test' phase after any tuning work!) So if the Tuner you use has access to a dyno, that effectively means that they can easily & repeatably test, measure, & check how well their actual
'tuning' work has improved the way your engine runs; but for a Constant 4WD like your 80 Series, they'd need a 4WD Dyno to do that! So really, the 'dyno' bit in 'dyno tuning' is just another tool in the tuner's workshop!
At the risk of preaching to the choir (but hoping to help those who may not yet be aware) the proper tuning of 'old school' diesels with mechanical Injector Pumps & pressure driven Injectors (like your 80 Series) basically boils down to finding someone to strip the Injector Pump & Injectors right down, check & 'fine tune' all the internals, the springs & their resistance/pressure, the timing, the fuel delivery volume & pressures, & the clearances/tolerances etc in the injectors & in the injector pump itself so that the system can & will pump fuel at the right pressure, deliver it at the right time, crack open at the correct instant, spray in the correct pattern, and atomise the fuel spray appropriately for the optimal delivery of power & fuel economy, all without compromising the exhaust gas temps & the internal cylinder temps regardless of whatever load & control inputs you may have placed upon the engine!! Despite what many might want to believe, it's NOT just a matter of throwing on a turbo & winding up the fuel delivery to get more power; doing that can be a quick path to destroying your engine - amongst other things, even just slightly too much fuel can cause high Exhaust Gas Temp's under sustained load, which might blow your engine quickly or maybe just gradually melt bits inside & destroy it over time!
Putting a new turbo & exhaust on your 1HDT will likely change the charge air delivery & the exhaust removal of your engine significantly, so even if it has been 'tuned' before &/or recently, you'll still really need a good diesel tuner to optimise the mechanical & physical internals of your fuel system & timing to make the best use of the changes to air delivery & exhaust extraction volumes & flow rates et al - and failing to do any of that properly could mean you'll end up looking for a new engine!! If you are looking for a good diesel tuner, Cooma Diesel, Berrima Diesel, West End Diesel are all places that have pretty good reputations for doing this really well, but I'm sure there are others out there now..... but IMHO tuning an old school diesel with a 'mechanically driven' fuel & injection system is way more involved & more of a black art than tuning a computer controlled CRD!