the stock turbo will say ct-26 on the compressor side, whether or not its been upgraded, idk, some of the other guys here will be able to tell you. a blown head gaskets will allow oil to mix with your coolant and vice versa. it will also show as white smoke coming from your exhaust. a way ive been told you can see if it is blown is to start it cold with the radiator cap off and let it warm up and see if bubbles appear where you can see, bubbles are bad. the reason behind the BHG is the torque specs for the head bolts, they were undertorqued from the factory and weren't corrected in the manuals for the cars. the book lists it as about 58 ft-lbs IIRC, we all recommend atleast 75-78 ft-lbs of torque.
link to pic of turbo(not installed)
http://www.google.com/imgres?imgurl=...ch&um=1&itbs=1
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87 supra, 7MGTE, head gasket and turbo replaced, runs and boosts! fixing wiring odds and ends, then storage for a year basically...then comes big money cash in er, lookin for 500+ to the ground and a very sleek, sexy mkiii