All i know is one is newer than the other but thats it. What do they do and whats the difference?.  Ive bought a 1980 series 1 and wondered which electronics will it have and what is the newer one doing differently.

Congrats on the new series, Jazzy!  
 
Im pretty sure the PF5 electronics won't be found on anything past '73-'74..... The PF6 has evolved a bit, but thats almost certainly what's in there...