I finally swapped a TH350 in place of my ST-300. I've only driven it with the new tranny a few times before the weather got lousy. It's amazing how much of a difference the lower first gear makes. Also, with three gears the engine seems to spend more time in the sweet spot of the power band.

There was nothing wrong with my ST-300, but I hated it. Wind it up to 70MPH in first and wait for the shift.

I don't think you're going to enjoy the project on ramps though. Put all four corners up on jackstands and use your floor jack to lower the transmission.