Newby questions...

[72charger]

High all. I am considering purchasing an 87 Supra non-turbo from a guy. It has a major coolant leak and he thinks it's the head gasket despite that there is no coolant mixing with the oil. I read on here that the coolant passage can simply leak into the combustion passage and just get burned away so maybe that's what is wrong. It also has a check engine light on. Not sure why, the car seems to run fine. I am a newb to Supras but not to cars nor to turbos. I am considering buying this car and replaceing the head gasket asap, and diagnosing the check engine light. Then I'm just gonna mess around with it until I have the money to do an overhaul under the hood. How much boost can I run in the stock NA motor? I plan to buy a relatively stock type supra turbo, intake manifold and full turbo exhaust. What else do I need to do it. I know the compression is higher on a non-turbo motor. What all would I need to do internally to the motor to run 15-20psi? I know it will need low compression forged pistons but what else?

Also, are there any motor rebuild walkthroughs or guides for a turbo application? Thanks for any help you can give!