There are many variables as to the possible method that was used to connect your current throttle set-up, so your question is kinda hard to address without actually seeing what you have.
Is the Dodge bell-crank throttle set-up still intact and then the Ford accelerator-cable connected to that ??
If so, then there is the problem.
It is best to eliminate the bell-crank and connect the accelerator-cable directly to the throttle-lever on the injection-pump itself.
You will have to fabricate a bracket to accomplish this.
You will also need the appropriate size little trailer-ball-looking thingie that the cable snaps onto; I got an assortment of them --- HOLLEY brand --- at Advance Auto.
Also, it is best to carefully eliminate that red plastic sleeve that is on the cable-end.
My accelerator functions as well on the Cummins as it ever did on the IDI.