I did install a higher RPM stall torque converter and a shift kit in the tranny. Then also based on TV (throttle valve) cable adjustment, I have the shifting set to points I felt were good or comfortable for my driving style and "butt in the seat" feel. There could be some tweaking for people who want a bit different feel or response. But you're right, under lighter throttle it does shift earlier (about 45 MPH). Under a heavier throttle, it shifts later. And if it's in OD (4th gear) and you romp it, it will down shift and disengage the lockup. There's a balance there when you adjust the TV cable. Too little and the shifts are soft, the fluid pressure is lower (not good generally), and no kickdown on harder throttle use. Too much or too tight on the cable and the shift kit makes the shifts harder and later. When first making trial and error adjustments, it was scratching the tires when it would shift into 2nd even under lighter throttle use. So the shift points for me have been set based on that balancing act of good response when hitting it hard, not too hard of shifts under normal throttle use, and kickdown when wanted/needed - all coupled with my shift kit and higher RPM stall torque converter.
You made the comment about the lockup occurring "between 3rd and 4th gears". In the 700R4, the lockup won't occur until you are in 4th gear due to how the lockup solenoid is wired. The +12 comes in from the external connector (through a manually operated switch or the brake light switch as in my case). But the ground for the solenoid is internal to the transmission and is operated when the tranny shifts in/out of fourth gear. So as long as the +12 is there, shifting into 4th grounds and activates the solenoid and shifting back out of 4th disconnects the ground and turns the solenoid back off. Now you can add an externally controlled ground via the eternal connector and then use that lock it up at any time you want (manual switch, external tranny controller, etc).
I thought about the GPS speedo with my gauges, but decided against it for two reasons: (1) Additional cost for the GPS sensor since it was not included in the kit. The existing pulse sensor was already included and ready to go and already fit the D300 connector; and (2) mounting location for the GPS sensor. Research indicated it wouldn't work well mounted under the dash or hood. It needed to be mounted on top of the dash or somewhere more obtrusive where it could get reliable satellite signal. I didn't want that mounted out visible somewhere. I've had no issues with the pulse sensor and it works just fine.
