I really wish I wouldn't have sold my other 5756B, I had one sitting around for quite awhile.
These are all hard things for me to confirm from either end, though I do know that mine is a 10 spline input shaft. It's too cold for me to pull my trans and have a look and the seller "is out of town". I may have pictures from the multiple times I've had to pull my trans. I'll look around in the garage, I hope I still have the alignment pin for my clutch. I know that I have a dual disc clutch and can probably find the specs for that online, they were not very common from what I've read. Detroit Clutch Masters told me it was one of the first dual disc clutches when they rebuilt it.
I do have an adapter on the back of the motor/front of the trans. It's about 4-5" thick or so and my starter bolts to it.
I'm in the midst of trying to wrap up a lot of things on my old Willys truck I've been building since that fits in my garage. If I do pull the trigger on this trans it will sit until it's warm enough out to do a swap.
Here is a link to a place selling the 3053A that I came across while looking
https://www.boyceequipment.com/transmissions . It states
*The 3053A Spicer Transmission fit almost all Diesel applications as well as most Chevrolet engines. Dodge and Ford applications are more expensive to install.*
Considering the price the seller is asking I maybe willing to take the gamble.
