Technical educated me on how auto trannys, shift speed and rpm's work

I have a 1963 ford country sedan.

352 - lightly hopped up - holley 4bbl, headers, cam, pertronix billet disty.

brand new c6 ****** - with kick down. no AOD.

I think my rear gears (final drive) is 3:1.

The car seems to shift out of first, into second just barely out of idle. Like at 5 mph. From there it's sort of a dog. Seems like it should hold 1st gear till atleast 15 mph or so.

What controls this - and how do I dial it in?

Edit- and I should add - the car idles fast - so maybe the pump in the ****** that shifts gears has too much pressure because of this?

 

I think on a C6 you need an adjustable modulator, while on a GM auto you can manage this with a governor recalibration kit. Here's the B-M kit I used on the T350 in Joyce's pickup... http://www.jegs.com/p/B-M/B-M-Governor-Recalibration-Kit/751474/10002/-1

 

probably more info needed , is this at WOT? is this at a slow moving off from a stop?

 

Even in second, the torque converter should let it pull. Is it shifting to second or directly into third? Try shifting it manually starting in low, shift to second then drive. What does the transmission builder say?