OK, I don't claim any expertise, so consider this just one more person's opinions. The basic problem is the gas pedal. If the original that was damaged felt right when it was in place, then you need to consider its geometry when replacing it. In other words, you need to consider the following:
- The top arm of the pedal needs to align with where the cable enters the footbox.
- The pedal pad needs to be where it is comfortable for your foot.
- The pivot point needs to be where the ratio of the length of the two arms (above and below the pivot point) is the same on the new pedal as for the old. For example if the upper arm was the same length as the lower arm on the old pedal, they should be the same lengths on the new pedal to achieve the same pedal feel.
- Satisfying all the above will tell you how long the pedal should be and where the pivot point should be mounted.
The photos make it appear that the replacement pedal you have is shorter than the original, meaning the pedal pad will be higher off the floor. If that is a problem, perhaps you can fabricate a longer arm for the pedal. ... I'm guessing that the shop that provided the pedal assembly intended to attach the pivot block to the footbox somehow. If there are no obstructions on either side of the footbox, and if the fiberglass is strong enough there, perhaps it can still be used. If not, it wouldn't be too hard to fabricate a larger metal plate (to spread the force on the fiberglass over a larger area) with a bracket for the pivot pin welded to it at the right place (up/down, in/out, left right).
One other idea came to me. If your footbox is strong enough and has room above the pedal area, you might be able to hang a top mounted pedal from someone like Tilton. If that is possible, you could reroute the throttle cable to exit from the top of the footbox and significantly reduce the length of the cable assembly.