I have a 78 Grand Lemans with the 305. my goal for this Memorial Day is to convert my two cable speedo to a single. and removing the box. first question is, what is that box? (service interval counter, cruise, etc?) and if I remove it, will it affect anything like mileage counting or of that sort. and second question is, if someone is familiar with this, what size single cable should I be looking for? haven't had the chance the measure both cables since my car is a little of a haul from my home. quick responses would be ideal cause i leave work within an hour and am looking to go pick the part up at an auto parts store. thank you everyone!