I’m definitely a fan of Type F no doubt. But in a street car Dex/Merc is way to go in my opinion. It’s not an issue if you switched to Dex/Merc right now. It may not make a HUGE difference with what your experiencing but it’s not going to hurt. I didn’t realize it was mainly a street car. I would put a Dacron filter in as well.
I guess I explained it poorly, basically pull foot back off throttle and bump into 3rd real quick, kind of simultaneously. I can understand a true coast you would feel the overlap more. If you don’t pull front pump and drum out, I’d at least verify the second gear servo has dual springs, and if it doesn’t, I would certainly make that change. That will help the overlap because it will allow the band to release quicker.