Depending upon the Muncie, it should be a direct swap. It’ll need to have a 26 spline inout shaft and 32 spline output shaft. You’ll also need proper shifter linkages too.
You can always buy a used ST-10 in excellent condition. I’m not sure what the ratio here, but this may be an option for you if you need more than just the trans.
http://forums.maxperformanceinc.com/...d.php?t=843195
And the ratio doesn’t affect installation. It’s simply torque multiplication in gears First to Third. It also affects power rating, which you’ll see in the Richmond chart.