What options for O/D behind a S/6?

My daughter and I pulled everything out of a full sized PU w/6. the aluminium 4 spd (3 speed w/od) has been in for 8 years. I had to re-clock the Z-bar but everything fit in her 73 Dart. A body peddle assemblies are easy enough to convert. With a new clutch kit we had less than $200 in it. She loves rowing through the gears ;D