coolent pooring out between block and firewall?

Its your car, your engine and your money, so work away fella, the only thing I would say is that a gasket is meant to be the weak link between head and block. I would rather blow a head gasket, than crack a block with a fully forged build in it.

 

http://www.chevyhiperformance.com/techarticles/0608ch_performance_head_gaskets/index.html

Good read on head gaskets in general. Does mention in there that one application may benefit from the copper gasket where another application may not.(If I read that right.)

I did read alot about ringing the cylinder head/block to accept an o-ring(if needed. Depends on Copper Gasket). Also looks like the copper gasket is going to set you back a few more dollars than normal.

Biggest thing you may run into is you are going to have to get a company to manufacture a copper gasket just for your car. I didn't see a 3SGTE listed, but I wasn't looking that hard either.

I understand wanting to get the bigger and better thing, but in this case you might be just re-inventing the wheel. MLS gaskets are tried and true in this particular application. But, I''m not against you trying it out and letting the rest of us know how it works out.