Here is the book that you are looking for, it is the best reference for your 65 mustang wiring. This is not my auction nor do I know whose auction it is, I was just referencing the pic so you could find it. Any mustang supplier should carry it ie: www.californiamustang.com, texasmustang.com, virginiamustang.com, NPD, etc
http://cgi.ebay.com/ebaymotors/1965-Ford-Mustang-Electrical-Wiring-Assembly-Manual-65_W0QQcmdZViewItemQQcategoryZ34220QQihZ007QQitemZ170143431840
The pics are not huge but like I said, it is the BEST reference so I would recommend copying the page and blowing it up if you have trouble seeing it
If you have a specific question about the wiring, post it, I will be able to help you with it
Best of luck to you, hopefully the previous owner(s) didn't hack up the stock wiring too much