[Bored&Stroked]

Once you change to the later gears, then you need the later transmission top (like a 39). When you do this, you cause a few problems (all of which can be overcome - if you know what to do):

1) The "straight up" shift tower of the 39 top requires that you alter the original 32 transmission cover - taking about 5/8" of metal from the front of the hole
2) You no longer have a provision to mount the hand brake - so you'll need to buy a bracket designed to bolt to the 39 top and mount the 32 hand brake.
3) If you're using the stock 32 brake light switch - it no longer has the correct mounting holes - so again you need a bracket to allow you to use it with a 39 top.
4) Stock mats and any special carpeting may need to be modified - as the shift tower is now bigger, straight up and further forward.
5) You'll need to use a later shift lever - you can no longer use the 32 lever. Most folks like the "swan neck" 39 shift lever - but it definitely is not shaped like a 32 lever.
6) Depending on the later gear set, you may need to grind/clearance the inside of the 32 case (such that the front cluster gear clears the case).

Okay - that is about all I can think of! LOL

Good luck!
B&S