904 Lockup Transmission Adjustment Help needed

I do have it installed now, and it did make a difference. Not as much as I had hoped, but still much better in my case. The Mopar part # is 04186185 PLT/SPRG, and the label has a printing date of 1985, and an additional code that says 8 89 that might be the actual package date. My car shifted almost immediately into lockup at the lightest acceleration. I have a 340 with Comp 268 and Edelbrock 650 in a 1968 Dart Convertible, with small 215-60-14" tires that measure approximately 23 1\2" diameter and a 2.76 ratio. The car on light acceleration now will shift to 3d and not lockup until about 39 to 40 MPH using GPS. This works out to be about 1700 rpm and then falls back to 1500 rpm. At brisk acceleration the car remains in 2d past 40mph and then it falls almost immediately into lockup again. The package contains a heavier spring, but also a new plate that has two holes drilled in it. The one I removed was solid. I wonder if drilling the holes larger would increase the lockup speed, but that would be a guessing game. My torque converter also seems to be really tight and chokes the motor down whenever shifting the motor into drive or reverse at idle. 800rpm. I don't know if that makes any difference.