79 Cutty

Hello I am looking for some help and guidance. I am trying to fix up a 65 mustang for my dad. I am trying to change the tranny from auto to manual. It is a straight six and I was woundering if I do that how do I go about doing that and is there any major change or problems that I will run into? If it is possible to do w/o refinancing my house were can and should I start looking for parts and tranny? If you can help me I would really appreciated it and so will he. thaankx