I've looked into putting a 300 EFI engine into a EB. There are a few models of F250's that actually had a 300 EFI with a ZF 5 speed. If you found one it would be an awesome donor vehicle to swap both engine and transmission at the same time. If you had a automatic and wanted a manual that is.
Anyway I never bought these so don't know if they are any good but there are a couple issues of
Bronco Driver Magazine that deal with the 300. Issue 19 has an article titled "Installing a Ford 300ci 6 cylinder in an EB" and Issue 46 has an article titled "The Ford 300 Six - Upgrade Options" they might be helpful. It might take some extra work but think it would be a cool and unique to have an EB with a 300 and something I would seriously consider if I ever build a second EB, especially for a daily driver rig
Also check out this
thread if you scroll down rjlougee put a 300 into his rig the links don't work anymore

but might be able to touch base with him. Also check out this
thread for more discussion about the 300 on the second page there is a link to some performance parts for the 300's