Seriously. For whatever reason the replacement part is different. It's long enough to be used with multiple applications included the six cylinder. That happened on other parts too like alternators. This one is a little surprising because its physicly different than the factory part.
There's a few members here who have a greater understanding of the parts system.
@Vaanth and
@townsend come to mind
Production numbers and choices are not always the same as replacement, or service, parts listed in the parts catalogs as intended for dealer use. In some cases, production versus service number differences are documented, such as the case for transmission assemblies and alternators, and some wiring in the later 1970s. In other cases, such as the battery cables, the differences do not show in the parts catalogs. Part consolidation also occurred where one replacement part might replace multiple production line parts and/or applications.
The helpful diagrams in post #3 show the varied production cables for series C/D/E (1967/1968/1969) and the varied A-body references, but the simplified and consolidated parts catalog replacement is a single part to replace all for most 1968 and a different but still consolidated coverage for 1969.
Negative ground cable, part number 2525348, is a general replacement #6 gauge cable and it is long enough to fit multiple engine (including six cylinder) and body applications. 2525348 was in use from 1963 through 1968 (Imperial through 1966) to fit the A/B/C/D body lines for all engines, except 426 Hemi (more due to its larger #4 gauge than length). Due to the multiple fitment, this 28" cable is longer than the varied production cables and long enough to fit all the multiple applications.
In 1969 cable part number 2421199, a heavier #4 gauge, 30" cable was the service replacement for A-body and B-body (except 426 Hemi) applications as well as superseding 2525348 for earlier applications. The 1969 C-bodies reverted to the older 1962, shorter 23" replacement cable, part number 1879944, due to different orientation (this cable was also used previously on A-bodies). Imperials switched to another older, heavy #1 gauge, 27" cable, part number 1879949.
The A-body 8-cylinder production negative cable length was ~19" from bolt eyelet center to post terminal center. The longer 28" and 30" replacement cables could fit the larger cars and accommodate the longer length for the six cylinder engine.
In 1970, things became even more varied with battery cables, and the additional lead for body ground was added to the negative cables. The service replacement for A/B/E-bodies with 8-cylinder engines, except 426 Hemi, was a shorter, 23", #6 gauge cable. The six cylinder replacement was now a separate 27.5" cable. The shorter length, especially coupled with the separate body lead, enabled a drop back to #6 gauge, which the reduction itself, though adequate, was not the best engineering choice, but accounting demands often override engineering.
More changes continued through the 1970s. The 1970 negative cables stayed the same through 1972. A minor change occurred in 1973 with the wider B and C bodies. The A and E body cables remained the same lengths, but the cable style differed some. Cables continued to evolve although the negative cables continued to remain similar through 1980.
