The car has 220k miles on the odometer but the motor was rebuilt 70k ago? In that case I'd do head gaskets, being very careful to check for cracks between valve seats.

I bought a 94 V6 a few years ago with 130k on the clock and a blown head gasket. Which turned out to be a cracked head and a head gasket. The first "low miles" used 3.4 I bought turned out to be junk, costing me $600. Then i rebuilt the engine originally in my car. You don NOT want to go that route! Something like $3500 with bolting on the heads and everything else and installing it. I will not get my money out of this car unless i keep it for 10 years.
So, again, I'd pull the heads, check them for cracks, and reinstall them with new gaskets. In my experience it is the right side head that cracks for some reason.

 

Man, I hate to be a nay-sayer but something else that you need to weigh into the equation.

Being someone who has been burned in a very similar fashion I will agree with 1augapfel. If it was a recent rebuilt their might be a chance but some massive red flags here.

If a mechanic is getting rid of it chances are its more trouble then he wants to deal with (that's a bad sign).

If you do the work yourself, you can get seal kits and all the stuff for a decent price. One thing I've seen not mentioned is when you get it all apart, check to see if the heads are warped. It might of been ran and overheated, if that is the case then heads are most likely warped and throw the engine away.

If this is your first Camaro and if you do end up wanting to sell it, I'd at least learn as much as you can. It will help with future Camaro's