Heck, you could probably pick up an adventure path or two for 10 bucks or so each and they convert easily to the OSR rules of your choice. Castles & Crusades pretty much is the Rossetta Stone of the OSR ;)
I think the Codex Centarum is one of the few releases not included, and this is an very recent release, so I can understand why.
The Minotaur for Old-School Essentials
*Requirements:* Minimum STR 9, Minimum CON 9
*Prime Requisite:* STR and CON
*Hit Dice:* 1d10
*Maximum Level:* 8
*Armor:* Leather, including shield...