This is from Fordification.com
T-18,T-19
Another Granny-Gear transmission. These transmissions were installed in many 1965-1985 Ford pickups (as well as Jeeps and IH Scouts) as a successor to the T98. Ford used three different versions of this transmission, which is equipped with a 28-spline output shaft. Both the case and top cover are cast iron, with the top cover being secured with 6 bolts. First gear and reverse are not synchronized. It's replacement, the T-19, was used in '74-'88 Ford pickups and some IH trucks and is identical in appearance except has a 5.11:1 first gear ratio which is synchronized.
The T18 & T19 has a 1-1/16" diameter, ten-spline input shaft that has a stickout of 6-1/2" from the front face of the transmission. The pilot tip of the transmission measures .668". The front bearing retainer flange measures 4.850" and the bearing retainer tube is 1.432" in diameter. The front bolt pattern is the symmetrical Ford "butterfly" pattern; 8-1/2" wide by 6-5/16" tall. The input shaft length is 6-1/2". Checking these dimensions will verify that the transmission is a 1966 or newer model, precluding it from being the T98. The transmission can also be identified by its casting numbers cast into the driver's side of the case. T18s have casting number "13-01" and T19s have casting number "13-09". Case length is 11.875". Unlike the NP435, the PTO port is on the driver's side.