Which Yoke and leak questions

Hello,

I have a 1966 Barracuda Formula S with an A-833 trans. I have the small yoke from the 904 transmission with the number 2530892 on the yoke.

So after I restored my car and put the trans back in I had a leak at the rear seal so I replaced the seal 2 different times hoping that would fix it. It still leaked so last week I decided to get a different yoke as that is what most people say that if the yoke has any corrosion it will leak.

So I bought the mopar yoke P5007409. It has 2852236 stamped on the yoke itself. I tried to put that yoke in today. What happened was that the new yoke would not push in far enough to allow me to get the rear u-joint into the housing on the rear axle. It engages the splines just fine but will not go far enough in so I can get the rear u-joint in. This yoke is 7 1/2 inches long and has a shaft that is 5 1/8 inches long

So I looked at the old yoke and it is much longer 9 5/8 inches total with the shaft being about 7 1/8 inches but it has a step down along the shaft of the yoke, the step down area is about 2 3/4 inches, which I assume goes inside a bushing? inside the rear part of the trans. I also noticed that when I put the old yoke in that it pushes against something that feels like it is spring loaded. I need to push against whatever part that is inside the tail shaft to get the u-joint to go into the rear housing. Does this make sense?

Is my only option to try and get another yoke like my original? Or can I cut a step down in the new yoke that I bought?

Wondering what is going on here.

Thanks for the help.

Dave