yes, the Ford NP205 input gear is 31 spline.
and the Chevy is 32 spline for the th400...
but, and this is where it gets interesting...
the bearing sizes are the same for the OD of the input bearing.... as well as the size of the bearing retainer, and the bearing retainer bolt patterns, and the input shaft seals... sooo.. you can use a chevy input in a ford case, a ford input in a chevy case, as long as they are the right sized bearings, the LARGE bearing. IE, a th400 to np205 roundfaced case like the Ford np205 roundfaced case only with a passengers side drop and a slightly different bolt pattern. This also allows you to clock it a bit for clearance, if needbe. No adapter rings needed.... bolts up to the pattern YOU drill in the face. The ford pattern.
Basically, what Im telling you is that the parts are capable of interchangeability for input gears between the Ford NP205 and chevy (th400) NP205. if you want to put a married np205 in behind an AOD/E40d that has a 31 spline output, and a ford pattern adapter, you can use the roundfaced chevy case. This case was used in 1987 to 1993 chevy one tons. it was used with the 4 speed, with a longer input, and with a th400 with a longer input. but the early shorter input will work, too.. as will the ford NP205 input... behind a ford trans... with 5 or 6 holes drilled.
How do you get it drilled right? This is the fun part.
You need an input bearing.
you need a bearing retainer.
you need your adapter.
Install the input bearing, and bolt the bearing retainer onto the case to hold the input bearing in place. This will ensure that the bearing is located, that the bearing locates the bearing retainer, which locates the adapter.
rotate the case to where you think it will clear the trans, where it is most appropriately clocked for your application.try to get one of the original holes lined up, if you can. install one bolt, to hold things in place. then transfer punch the rest of the bolt holes into the face of the case. Drill and tap these holes, and install the guts of the case.... at least it sounds easy.
I did it in about 3 hours (reassembly), but i had a nice little parts washer and a clean bench to work off of, after the drilling and tapping took place. Took my time, followed the book, and thats about all there is to it. Of course, I did it the other way.. I pulled the guts out of a round faced NP205 for a chevy, and installed them into a Ford NP205 behind a th400.
total cost? well, i traded some scrap metal for a ford np205.... I had the input.... the roundfaced chevy np205 was given to me out of a wrecked truck... I had to pay 50 bucks for the chevy adapter... oh... i bought a new set of seals for the bearing retainer.
Advance adapters could have sold me the same parts... that are available from the factories... for a whole lot more..
whichever you do, good luck.
