Did you get the PM I sent you about a company that makes adapters to run a W58 manual behind the Lexus V8 engines?

The HG issue w/the 7m is/was similar to that of the 3.0, i.e., designed for an asbestos HG and not being allowed to use one here in the U.S., and then not compensating w/a higher torque value for the head bolts.  80ft lbs is what is recommended now for the 7m HG.  A lot of MKIII Supra owners have been able to re-torque the head bolts and have gotten good life out of the oem/oem style HG.  The other issue w/the oem/oem style HG is when turning up the boost, the paper gasket can't w/stand the pressure for long and then lets go.