I hate to say this.. but I will... It seems you guys running big power through the R154 are STILL breaking them even after using Marlin parts. Mind you, I have an affinity for this gearbox because of it's universal use. However, there comes a time when it's "fish or cut bait". All of the discussion about straight cut gears to possibly fix the problem is, I think, like putting a band aid on a gash. I think a better idea would be to abandon the R154 in mega horsepower applications and move on.... That being the case, a better alternative would be to have someone cast bellhousings for the 7M or 2JZ to bolt up a T56 or Tremec TKO direct. The only guy I know that could do that is Bill Hincher.... if there was sufficient interest.
http://www.billsautofab.com/recent_mit.asp
Greg
http://www.billsautofab.com/recent_mit.asp
Greg