Winter Upgrades (Feedback wanted)

The engine was originally dyno'd with 2.125" headers. I already bought the headers

The current convertor doesn't work with this new engine, way too tight. It's an Art Carr 3,500. I have no choice but to change the convertor. I already bought this.

The belt drive will be played with once, on the dyno. Wherever it likes best it will stay.

The new carb will be tuned on the dyno as well, then fine tuned in the car.
Sounds like you have a decent plan!