OUCH!!!
Having been bitten by the HG monster myself early this year, I know how painful it is!
If you're just looking to get the car running as a short term solution, then I could see going the route suggested by Kurt Sr., but I don't think it's a good idea in the long term. Most of those 'stop leak' additives don't only block the source of the leak but they often times plug up the rad and heater core somewhat also. Some are worse for this than others. Also, when the HG's usually go, it's because the fire ring has failed, and then combustion bleeds through to a water passage between the head and cylinder block mating surface. Often, part of the fire ring gets sucked into the cylinder opening. This can also lead to the piston coming up and contacting the fire ring. Usually this will only leave a 'highlight' on the top of the piston, but in cases where the piston to valve clearances have been decreased (1.8:1 roller rockers, extremely milled heads, etc.), this can make the difference causing a valve stem or pushrod to get bent slightly.
If you plan to keep the car long-term, then I suggest you start looking at fixing the problem properly.
Also, it is possible that the leak in the rad was the direct result of the head gaskets blowing. The rad could already have been weak from age, and the added pressure from combustion or compression being bled into the cooling system may have been enough to rupture it. You probably should take a good long look at the whole system to see the full extent of the damage.
Oh, and if you find that the oil has become contaminated with coolant, then you need to consider that the camshaft and crankshaft bearings might be on the way out too. Glycol and bearings don't get along too well!
I hope everything works out for you.
Best regards,
Sean