I found this Toploader on the Craig List. It supposed to have only 60 miles since it was rebuilt. This is the story I got when purchasing. The guy jumped in head first restoring a 65 Mustang and after he realized he's cruising rpm was up there he decide swap it out with a 5-speed.
I ran my numbers on David Kee's site and it's not a Mustang transmission. The tailshaft, C60R-7A040-C, does not look like the ones on his website, this one has both rear and mid shifter mounting holes drilled and tapped. The tag reads HEH-AR which is 1966 Fairlane with a 390, wide ratio 28-spline. But it's a close ratio 28 spline. The case, RF C5AR-7006-D reads 1965 casting used from 65-67. Wide 8 hole case.
I tried to fit the bell housing onto the transmission while it was sitting on the floor and notice the front bearing retainer on the transmission is about 1/8" too big to fit the center hole in the bell housing. I decided to let the machine shop cut down the retainer than opening up the bellhousing. This will give me an option to sell my bellhousing if I ever change to a 6-Bolt block.
The slip yoke from the T-10 does not fit on the Toploader. The transmission came with a yoke but not the u joint. I went to every parts store in town looking for a universal joint that had 1" caps on one side and 1.063 caps on the other. My T-10 used 1.063's all around. I finally found the part I needed only to find out it my yoke was leaking at the plug. I got a new yoke that took the 1.063 cap all around.
I was going to make my own adapter to move the shifter closer to the gear box but I took the easy way out and swapped the tailshaft housing with a aftermarket housing to get my shifter to fit.
The heavy duty transmission mount is made by Melvin's Classic Ford Parts. This is made from boxed and flat plate steel, all joints and gusset have a continuous weld. Looking at the picture from the other vendors website theirs looks like they used smaller gauge steel and stitch welded just enough to hold it together. I can't see any gusset for strength either. Kinda Mickey Mouse compared to Melvin's mount.
I'm using my old Hurst Competition shifter from the T-10 but the linkage rods needed tweaked to fit correctly. Reverse linkage was way to short being the T-10's reverse is inside the tail housing and not in the gearbox like the Toploader. After pricing new shift rods it didn't take me long to put on my thinking cap. One of the shift rods that came with the Toploader shifter was about to see some changes in its appearance. With a bench vise, cheater pipe and 6 lb sledgehammer, the new shift rod now looks like it got ran over with the lawnmower.
I notice the overall throw going into any gear is a lot shorter too, no more busting my knuckles on the heater controls. It took me a day or two getting use to a close ratio after years of driving a wide ratio gear box. The first thing I did was drove around town in 3rd gear. That was something I could never do with the T-10 transmission because it would always jump out of gear.