But this toploader 4-speed should work in my 65? (RUG BF)
It will most certainly bolt right in behind a small block as it has the right bolt patterns and is the proper length needed for a Mustang, but the shifter mounting is not directly compatible with what is used with a 65'. The 65' mounts the shifter at the rear of the tailhousing, whereas the shifter found on the Rug BF is mounted more forward. If you got the shifter with the tranny, it is worth a try. If not, you might be able to use a big block Mustang shifter mount adapter from an early 428 car which uses the forward 3 hole of the tailhousing, but it still may be too far forward for a 65'. I've compared the
Hurst BB adapter mounts to the Hurst SB mounts before and there is about a 1" difference in shifter location.
Alternately, you could
easily swap out the tailhousing for one from a pre-70 Mustang toploader with a small block and then you could use the stock or an aftermarket 65' shifter. The C4ZR-7A040-A tailhousings are pretty common (actually used from 64-73, but more common in the earlier years) and it is a very simple direct swap. All of these castings were 28 splines and the same length (14") as what you have.
The DOZR 7A040-A found on your RUG BF is seen on the top and the proper 65' Mustang C4ZR-7A040-A tailhousing is the on the bottom in the following photo:
Although the same C4ZR-7A040-A tailhousing is found on the older 25 spline toploaders, the tailshafts are the same as the 28 spline ones.
A C6OR-7A040-C or a C7OR-7A040-A tailhousing (with a 28 spline output shaft) will also work but you have to be careful with these as the same casting was also used for the 31 spline output shaft and thus the end was overbored for the larger diameter bushing and seal. The 31 spline tails are not interchangeable on a 28 spline shaft.