I just ran across an old Radio Shack adapter called PSX to USB. It is working pretty well with my original SG and Wireless guitar on Guitar Hero II and 80's edition.
There is a little lag which can be compensated in the calibration section. Also the downstrum is up and up is down. No biggie.
At this whammy bar is not working. But its the best solution i've seen so far. I paid a 1.25 on ebay plus shipping so you should be able to find one cheap.
Just thought I'd pass this along here for all of the people that bought the TAC Adapter (including me) and were hoping that would be the solution for GHII on the PS3.