One thing about the 3-speed transmission: Unless you have very deep gears you most likely will never see a '4th gear' before the finish line at the dragstrip. So the 3-speed was a very good choice for me as my cars never had deep (un-streetable) gear ratios out back. Yes they are heavy, but you probably aren't going to break it working it hard.
I have the answer to shifting it quickly: what I would call a 'pretty rare' NOS Hurst Inline Ram Rod shifter for this transmission. And it is for sale too !! Here you see it installed on a Saginaw 3-speed, and I'm quite sure it will work on a Muncie as well. I'm not finding any photos real quick of it installed on the Toploader, but I assure you it works there also since I still have my heavy Duty 3-Speed Dearborn that I would like to sell also.
djtech65@hotmail.com