Is the pivot arm visible in any of the pics i attached?
Why yes......., yes it is...... Look at the third pic, (bottom), the pivot arm that 'thing' that is attached to the throttle and distributor linkage at the top and is over the top of the spark plug wires; (they: [spark plugs wires] look to be yellow in yer pic), the arm has a bolt projecting from a swivel at the base said pivot arm is where the throttle cable attaches with a 7/16 lock nut that is also visible (I believe it is 7/16; if memory serves me). Do you have a manual? It would be a VERY good idea to get one!
Also how does the locking tab work with the plastic barrels?
Some 'barrels' are brass some are plastic depending on the vintage and or manufacturer of the cables. The shift cable goes below the throttle cable 'barrel' (adjusting nuts) which can be turned in or out on the treaded cable shaft to get the proper throw on the cables to match the project at hand, (throttle or shift).
Once both 'barrels' are in their respective places as you can see (in the top pic) the holder snaps the 'barrels' into thier fixed place so the cables are able to operate their respective task as commanded by the corntrol.
Some models have a 'key' that fits through a slot in the 'barrels' to hold them as I think my 1977 1500 had, (but it could have been my 1968 or 69 1250 since I have been playin' with both of 'em recently).
If you can find a similar vintage engine to look at it would help you a lot, although this should get you through the basic task at hand, (I hope).
One more note: if these cables were the same cables that did formerly corntrol yer engine, and said engine functioned properly I would assume the adjustment is still proper. (If it ain't broke don't fix it)
Good luck. JR
Thanks man I appreciate the help