I have a 4x4 mudbogger and I want to put a automatic just looking for advice on what to get the motor has a mild cam and headers and bigger carb

 

Unless you decide you need an overdrive which would be very expensive and almost non-existant, your choice is simple: a built FE C-6 3 speed automatic.
But it also depends on what your TC is: divorced or married case?

 

My transfer case is directly behind transmission how can I tell if it has a five in shaft or 8 inch

 

The tc is maried

 

I switched my 72 Highboy last winter, I used a C-6 with a divorced transfer case, you need a C-6 with a short tail-shaft, it will have a bolt on drive-shaft flange, you can use your existing short drive-shaft, you will have to have it shorten a few inches to make it work. To be able to use your current 4WD lever you need a tail-shaft from a 73 up F250 4WD C-6, it has the bolt holes cast in it for the lever to mount to plus it has the speedometer cable hole blocked off. Below is a picture of mine when I was do the switch over

 

What type of shifter should I get I want a floor shifter I put some pics but not sure how to upload

 

What type engine stall should I be getting