Transmission problems 84 f150
I bought this truck as a fixer upper and play truck to do a little muddin in, but its just given me problems and its the first ford ive owned and its done me well but im not gonna give up on it.
Anyhow getting to the point the transmission recently started slipping after i was stuck in a mudhole for a good 30 minutes after being pulled out i immediately drained the tranmission fluid and changed the filter. However it continued to slip and several experts told me a few different things it might be but im pretty sure the transmission is just blown....
First off i believe its a c6 but im not sure i need to know how to tell what it is?
Second if i buy a new transmission what different ones can bolt up to it (other than c6)?
Third would i be better off buying a rebuilt one, having it rebuilt, or finding a salvage one?
Thanks for your time and help



