If the instructions are as bad as the instructions for my SSBC front disk brake conversion or my Classic Auto Air AC unit (and believe me they were both HORRIBLE), I would guess that is part of the problem.
No kidding, my friend!
I did a CAA kit in my '70 Charger late last summer. The people that write instructions for many installations seem to write them for people that have already done them before. I fumbled through but made plenty of mistakes.
Same goes for the garage door opener install. Liftmaster.....GREAT unit, terrible instructions.