First, I'm assuming that you have the "Factory correct" brackets (see attached picture and Illustrations) ?
If that is confirmed, then, remembering that they are only illustrations, look at the two that I have attached. The first is from the 1960-68 Ford Master Parts Catalog. Note that it covers several Models, so it is not "Mustang Specific". The second illustration is from the 1966 Mustang Electrical Assembly Manual, which is "Mustang specific", although not for 1965. Possibly someone with a 1965 Electrical Assembly Manual (Tony ?) could Post it just to see if there are any differences.
The previous Post has a very detailed set of instructions, however, at a glance through it, appears to include a lot of non-original parts, which may or may not apply in your case.
Hope this helps,