Dunno What the going rate for Garrets are, but the shop I'm dealing with locally quoted me a range of $480-$650 for a Holset (depending on which one I wanted). Bummer is Holset is the polar opposite of Garrett, they want to keep all their data 'proprietary' (aka secret), so all the compressor maps I have seen are the same one (reputed by people other than Holset to be for different models). I have some pretty good annecdotal sizing references and I'm going with an overhauled Holset from a '01+ Dodge Cummins W/ auto trans (Holset, HY35, 9cm^2 turbine housing). I'm puting this on a 3.9L Turbo Diesel (238 ish CID), it turns 3600 max (governor defueling point). Not sure if that would fit your plans but it will make loads of boost (more than you'll want, Higher pressure ratios are what Holset's claim to fame is) and it comes with a waste gate.
I only bring that up as your 194 isn't that different size wise and you can pick these up fairly cheap (the Dodge guys take them off to upgrade, as the turbine is too restrictive once you get above several hundred diesel horsepower [aproching 1000 Lb ft] on a 5.9L [360 ish CID]). Diesels do run more air through the engine for a given power though, so I'm not sure how that would translate to a gas burner (less gas through the turbine = later spool, but on Cummins and Isuzu 3.9's they are apparently spooling somewhere around 1500). You might check Craigslist in your area.
Oh, I didn't catch if you were doing Blow through or Draw through, AFAIK Holset doesn't have a provision for a carbon compressor seal.
