Your stock SRT-6 transmission is kinda on the weak side for a modified SL55 engine. A valve body upgrade would help compliment the SRT-6 transmission. Rudy (Accelerated Industries) can answer all your questions. He chose not to use my modified SRT-6 transmission for the SL55 Carrillo-Weistec engine build that he's dropping into my SRT-6. Rudy chose to build up a modified transmission pulled from a V-12 cylinder Mercedes. Squirrel Crusher