904 build. Where to get kits?

you can go with a transgo kit. they have different style kits for what ever perf you do. I am just upgrading my valve body as we speak for my A-999
100% right on with the Trans-Go recommendation :salute:!
Their kits are the only way to fly when it comes to TorqueFlites , as they are designed for them specifically , and not based upon the Turbo-Hydro design ( not that I've anything against G.M. , nor any other manufactures ) .

I've bought and used Trans-Go kits solely since 1991 , and have been nothing but 100% satisfied with the performance of these excellent kits ; no 3rd gear application *CLunK!* when you let-off the accelerator !!