Russell,
Ok, so it sounds like you're just looking to replace the Ford 9" center carrier with one that contains a traction lock differential. Be aware that differentials that were OE-installed behind a high performance engine or a big-block may likely also have gotten 31-spline axles, which means 31-spline differential side gears. Obviously, 31-spline side gears will NOT work with your 28-spline axles.
Locating a center carrier with a 28-spline traction lock differential may be a tough character to locate (I know it would be around these parts), but there may still be some out there - somewhere.
Good Luck & keep us posted on your progress!
BarnieTrk
