In order to help you decide, we need to figure out what trans is best for your planned use of the Bronco.
What are you using the truck for?
Do you need over drive for the highway (your diffs probably have 4.10 gearing)
Do you want an auto?
Most of the swap "kits" are designed for V-8 or V-8 conversions, are you planning to swap a 302 or 351 into your EB in the future? ( the six cyl trans has a shorter adaptor housing than the V-8 trans.) I am not sure if there are even any swap kits available for the six cyl EBs.
Check out the Advance adaptors Website or any of the EB parts houses ( Jeffs, wildhorses, Duffs, Toms Bronco parts etc...) you should be able to find some good info at any of them.