My donor build uses a 2007 Mustang motor and gearbox along with a 2017 Mustang GT IRS rear axle dropout combo, for which FFR has no driveshaft. These later 3650's have a flange output rather than a slip yoke, so a short driveshaft with slip yoke for assembly is necessary. I thought I should post this if other builders are using these newer boxes, as I was able to source Flanges, Universals and Slip Yoke very economically from DriveshaftParts in Florida. These folks were really helpful.
Photos are of driveshaft and gearshift modified to locate it forwards instead of back in the Mustangs.