I have it adjusted so at WOT the lever on the trans is maxed. It has a holley 670 aveneger and it has the special kickdown arm that holley offers for mopar.
The adapter just gives the linkage a place to hook to. I'm sure you're not getting full travel. If I change from the stock AFB to a Edelbrock carb on my 66 Dart I have to re adjust the throttle cable to get full throttle. Anytime you change anything you may have to modify the linkage to make it work properly. tmm