I mostly know about the T5 transmissions found in Chevy S10 and GMC Sonoma trucks. Camaros and Firebirds used them too. They have overdrive and can be made to bolt right up to your bell. However, you would be changing from column shift to floor shift.
A Muncie T10 4 speed would add another gear but final drive is still 1:1 so you would not gain anything.
Some GM vehicles used a 3 speed with an overdrive that was solenoid operated. I know they are very nice if you can find one.
