[computerworks]

Took a quick look at the Registry to provide a few more facts about wide-hip / narrow-hip 427's.

Remember that, originally in 1965, the intention was to build 100 Comp cars...but that didn't fly...ending up making 51 Comp rollers and a few chassis-only's.
When they began making Street 427's (CSX3101), AC still had panels from the Comp design (big rear fenders with flares) in the pipeline, so they were utilized on the early street cars.
However, the street 427 used 7.5" wheels in the rear, instead of the 9.5" ones on the Comp. The boys at SA felt that the smaller wheels looked lost in those big rear fenders, so they initiated a re-design of the rear end...removing the flare and changing the profile slightly. CSX3127 was the "narrow-hip" prototype.
Somewhere around 40 of these cars were made; unfortunately, dealers and customers felt the new design took away some of the .... er,..."sensuality" of the 427 body and didn't like the look.

...so, they reverted back to the "wide-hip" rear for the rest of the 427's production life.

So....the "rarity" is the narrow-hip car... the wide-hip was in the majority.