differences in 727 transmissions

IMO the best ones to get are the 71-73 model that came behind a 340 but their not always easy to find. They have the wide front stator bushing, part throttle kickdown, 4 pinion planetary gearsets, and 4 clutch discs in each carrier. Many of the newer units used 3 pinion planetaries and less clutch discs in the carriers. HD truck or motor home trans are also good ones because they usually have 4 planetaries and 4 disc clutch carriers but some have a bolt on yoke instead of slip yoke and if you have a factory floor shift most truck extension housings don't have the necessary bolt tabs to bolt the linkage to but you can easily remedy that with a extension housing change

You also have to keep in mind that if your trying to piece together a strong 727 that the spline angle changed in 76 so you have to use the correct year span front planetary set on the output shaft that your using.