If it is the normal earlier Muncie it'll bolt in exactly where the Saginaw is but the reverse selector rod is shorter. You can use the same shifter. The rear mount may be in a different location for the Muncie IIRC but I can't recall exactly - you'd have to measure, and the Muncie has the speedo cable on the driver's side so you need to get a shorter speedo cable and route it through the 6cyl speedo cable hole under the booster and put the bung across to the V8 hole.

If you get a later Muncie with the fine spline input shaft and bigger output shaft you'll need a different clutch plate to a Saginaw and the box is 3/4" longer. It uses a TH400 yoke thus you'll need a different tailshaft. These later Muncies were designed to fit exactly where a TH400 fitted whereas the earlier ones were designed to fit where a TH350 or Powerglide fitted.

Edited by user Tuesday, 19 January 2016 6:28:13 AM(UTC)  | Reason: Not specified

I always wondered why there was only 1 x tailshaft for HQ 350 sedan and coupe, and this extra length will be the reason why. From reading US sites it appears the pre 1971 Muncie was designed to fit where a Powerglide or TH350 fitted, but 1971-4 were meant to fit where a TH400 fits. It looks like the T10 and ST10 are the same ie ST10 uses the big 32 spline yoke like the 1971-4 Muncie.