I am not sure what kind of heads you have, but the Edelbrocks have heli-coils in them right from the factory. In fact, IMHO any threaded aluminum parts should have heli-coils in them wherever possible from day one.
I'll bet the v/c are leaking because they are hitting on the intake runners, not allowing proper crush on the gaskets. Almost every aftermarket v/c has to be modified to remove the interference.
The heads are Edelbrock Performer RPMs. I didn't realize they had those heli-coils in them. If I had I wouldn't have been so gun shy tightening the bolts. It's awesome they have them and I totally agree that any aluminum parts that have threads in them should be done that way.
Thanks for the suggestion 69_340_GTS but I'd already notched the valve covers to clear the intake runners when we first installed them so I was certain we had clearance. - And they didn't have any leaks until I re-used the old gaskets. The leaks that did start were on the exhaust sides of the valve covers and I could see that the header flanges had plenty of room between them and the covers. The new gaskets with the added sealant took care of our oil leaks. I'm not sure if the old gaskets were too compressed or if they hadn't been properly sandwiched between the rail on the heads and the covers. At any rate, we drove the car for about a half hour today and were leak free.
The tti headers we installed were bought used and had been hammered on in several spots for extra clearance. One of my fears was that they might have been so bent that they weren't mating flush with the heads. - They only clear our mini starter by about 1/8". There was no way we could have run a full size starter with them. Despite my concerns we're now leak free on the exhaust system now! - So I'm still thinking I hadn't torqued them down tight enough.
We checked the gas tank and could tell that the leakage there was coming from the top of the tank. We'd put a catch pan beneath it overnight and caught about a cup of gas. The plan right now is to continue with our tests and tunes and ignore the tank problem until we use up most of what's inside. The leak is only an issue when the tank is totally full. We'd thought we had done a great job sealing the access hole we made in the top but obviously it wasn't good enough. I'm still uncertain if I'd put sealant on the threads of the bolts that went into the nutserts. The tank may also have bowed when it was strapped into place.