What applications use SB 727's?
Any Mopar car or light duty 2wd truck or van (and HD trucks, vans, or RV's that used a 1 piece driveshaft) with a small block will bolt up and were all the same length but the 65 and earlier units were cable shift and the 66-67 units used a smaller converter register and different input spline count so stay away from them. You need to look for a 68 or newer trans. IMO 71-73 were the best years. Not all 360's had a 727 behind them.
If the cars your using them in have a factory floor shift make sure the extension housing has the necessary lower bolt eyelets where the shift rod bracket bolts too. Not all extension housings had the eyelets. If their column shift cars you can use any extension housing.