A833 In Truck
If the transmission is truly from a Road Runner, then the front bearing retainer should be 4.80". If that's the case, the 5.125" OD retainer is a bolt-on, unless it's a fairly-rare, early, small-retainer-pattern case (307 bearing). That makes it a bolt-in to the original bell, using the OD shifter though some mucking about might be necessary with the 3-4 lever/rod. I'm not sure if it's as simple as flipping the 3-4 lever. It might be.
If the transmission does have the small retainer bolt pattern, swap it to a 4.35" retainer. Then use a 1972-'75 non-OD LA car bellhousing (casting #3515734), along with the 1976-'80 2WD truck A833OD ball stud bracket that mounts to the bellhousing (it is not the same as the A/F-body part). The bell's fork and pivot should work fine with the truck linkage. You can't use the truck's clutch fork in this bell, since '81-'87 truck clutch forks use a ball-stud mount rather than a fork bracket.
Brewer's Performance will be able to provide anything you need that you haven't already got.
If the transmission is truly from a Road Runner, then the front bearing retainer should be 4.80". If that's the case, the 5.125" OD retainer is a bolt-on, unless it's a fairly-rare, early, small-retainer-pattern case (307 bearing). That makes it a bolt-in to the original bell, using the OD shifter though some mucking about might be necessary with the 3-4 lever/rod. I'm not sure if it's as simple as flipping the 3-4 lever. It might be.
If the transmission does have the small retainer bolt pattern, swap it to a 4.35" retainer. Then use a 1972-'75 non-OD LA car bellhousing (casting #3515734), along with the 1976-'80 2WD truck A833OD ball stud bracket that mounts to the bellhousing (it is not the same as the A/F-body part). The bell's fork and pivot should work fine with the truck linkage. You can't use the truck's clutch fork in this bell, since '81-'87 truck clutch forks use a ball-stud mount rather than a fork bracket.
Brewer's Performance will be able to provide anything you need that you haven't already got.