Originally Posted by Genob4c
I'm sure many of us here know that the Z28 was originally a trim, the RPO being Z28. I think the last year for that was 1974. There was no Z28 for 75/76, then the 1977 1/2 Z28 cam out as a model, not a trim (RPO). I'm pretty sure this is correct.
From a recent interview with Engine Labs.
"If youíve been paying attention over the years, youíve noticed that all of GMís engine codes start with L, while all the transmission RPOs start with M. Suspension packages all start with Z
. There are no more hyphenated designations, either, which is why the new LT1 is not LT-1 Ė although there was a strong push internally for the hyphen, according to Read. Only in the case of the Small Block engine, however, did anyone outside of the RPO naming group have input on a new code name. For you bread-and-butter Ecotecs and V-6s, the RPO group names them and thatís that."
The original RPO was for a handling package. It only became a trim option in the neutered 70's & 80's cars.