A couple of years ago I purchased a built TR3650 as part of a group of parts. The seller claimed it was built with upgraded components and it had a tranny dyno sticker on it claiming a rating up to 750. The TR3650 operates really well in the 99 GT now but I'm planing a build that should come close to doubling the HP & TQ. I noticed the tranny only has a 10 spline input shaft. From the little research I have done it seems like 10 spline are okay up to about 500 and above that an upgraded 26 spline should be used. Who's pushing what kind of power with a 10 spline....& what is a safe level keeping in mind it will need to endure drag strip abuse.