When I had 440-1 heads , and 528 (4.15 x 4.5) I used to leave on a plate with a .070 jet and progressed a fogger ( .036n .026f) at 3300lbs it would run 5.30’s at 130- 133 . That’s was 3.70 rear and 3 speed t400 stock ratios .
If I was you I’d be looking at a plate or ? Something for a second stage or a better controller and more jet in the kit you have .
Fastest I went with a 727 was 8.38 @ 160 . That was at 3550 lbs , sorry but I don’t remember the 1/8 numbers . I’m sure a 727 can handle more than 950 . Only weak part of the 727 is the sprag , and that’s more about breaking it on the starting line than downtrack
It’s really do you want to invest in a 727 ? Eventually you will outgrow it . Best for you might be a glide with a 1.82 or 1.78 first and a dump valve to help with the 1-2 rpm drop
I have a OEM case t400 from rossler , I called him to just get a 2nd gear leave valve body , and I ended up with a Reid case 2 speed $$$$$ 1.49 first with his dump valve set up