The T56 is strong, but can be broken. My GTO will be tuned to 550-600 RWHP w/ twin turbos [change from STS rear mount; currently underway] and I am not worried, BUT this is with 19" wheels which will not stay hooked up.
For my 66 'vert project, I have a TKO600 which is a very strong tranny, but will likely go the MMR route for more robust internals. They are doing some excellent mods [from what I've heard] for the TKO's.
Viper spec is expensive, but there are other approaches to beefing up the T56. The 6 speed is nice, but I am not so convinced of the need for an older car. And yes, it is physically a large tranny to deal with [having recently dropped mine when I put in a new clutch].
For my 66 'vert project, I have a TKO600 which is a very strong tranny, but will likely go the MMR route for more robust internals. They are doing some excellent mods [from what I've heard] for the TKO's.
Viper spec is expensive, but there are other approaches to beefing up the T56. The 6 speed is nice, but I am not so convinced of the need for an older car. And yes, it is physically a large tranny to deal with [having recently dropped mine when I put in a new clutch].