Quick question prior to ordering parts

[Grandavi]

I mentioned before, I bought a 90 Supra with a 7mGTE that is supposedly with a BHG. Now... I look at the car.. look at the former owners handy work (abysmal) and question the diagnosis.

So.. I put an upper rad hose on the car, filled it with fluid and then took it for a drive around the block. The oil is dirty, but I dont see any antifreeze in it. No white smoke coming from the tail pipe. I spun up the turbo.. it works adequately.

Then, I park it (this is just a one block cruise). The heat came above the bottom "C" so it was warm, but the car is pissing antifreeze out of the reservoir.

So... I take the rad cap off of my 88 and put it on the 90 (after it cooled and I refilled the rad with antifreeze). I took it for a spin again (the reservoir is filled mind you... not at the appropriate level because I didn't empty it) and no leakage. I dont see any signs of a BHG, but am still assuming it is bad. After driving it around the block (twice this time), I have fluid leaking from the reservoir (it was overfull and the cap isn't sitting on it tightly .. in fact.. I dont even think its the correct reservoir cap for this car.. lol.)

When I run the car with the cap off, I can see the fluid flowing across the top of the rad. Its gunky, so either the head gasket IS blown or the cooling system is in dire need of a flush. So.. that leads me to the question

A BHG will not make the car over heat.. or will it?

A bad water pump would leave the fluid motionless (unless there is something I am not aware of) so the pump should be functioning. The thermostat may be stuck, although that usually results in an overheat condition or a "wont heat" condition. So it shouldnt be that (the heat has never risen more than 1/8th of the way up the gauge and I have not driven for more than 2 blocks with it)

I think I have no choice but to tear off the top of the engine and assume the worst but should I flush the cooling system first? or just wait and do it after?

I have not done a headgasket on a 7MGTE yet.. so this will be a learning experience.

Also, I have an opportunity to pick up a 7MGTE (with turbo) with about 80k on it (shipped from Japan if I understand everything so far) along with a R145 Trany from a warehouse that is clearing them out. They want 690 for the engine, 275 for the tranny and will deliver it to my garage.

Good deal?