There are a lot to say here – but only a little that applies.
When F's first came out, they used the old style speedometer gear housing – that I will refer to as “metal”. Mid-year, or closer to '77, they rolled out the new style, which I will refer to as “plastic” - but supply problems kept Chrysler from using plastic 100%. I have seen '78's and '79's with metal (but not a lot) – so it mainly depended on what supplies they had on hand.
(see post 2 for pictures)
In addition to the “metal” vs. “plastic, you also have:
Early vs. non-early F/M-body, which uses a different end at the speedometer head:
Metal clip is top, plastic clip is bottom.
The "speedometer head" ends are the same – just the cable end is different. I “think” all '76-77 F/M's use the metal clip design (clip is on the plastic housing, as shown):
I “think” all other FMJ's used the cable end that has the clip on cable. If you can reach up behind the speedometer head, you can feel either the metal clip (which is pushed towards the head (or driver) to release the cable) or the plastic clip (which is squeezed at the end to release) – you can tell which design end you have by feel.
The next difference is if car has cruise control, or not. Cruise cars have two different cables whereas the others have one long cable.
Factory cables have a hex end at cruise servo and/or at metal housing, like this:
Aftermarket cables typically have a round “nut”. I've used lots of aftermarket cables and haven't had any issues, to date.
These are four common aftermarket cables, currently being sold today:
AYP-891 or Pioneer CA-3030 (what I think you already have)
AYP-879 or Pioneer CA-3024
AYP-802 or Pioneer CA-3002 (what you want - if you have cruise)
Pioneer CA-3014 or CA-3027 - which is 80". This is what you want if you don't have cruise.
The only ones I don't see made aftermarket is with the early F/M metal clip ends. I still see NOS versions out there – but not hard to convert the more popular plastic clip ends.
To answer your question, if you already have and plan on keeping cruise, you want cable AYP-802 or Pioneer CA-3002.
If you don't have (or want) cruise and you have the more popular plastic clip – then you want cable Pioneer CA-3014 or CA3027.
BudW