They were "computer selected springs"... I do not know what GM's RPO code breakdowns were for individual spring rates/heights and have never come across an accurate GM breakout of those.
Based on bits Ive read and been told, this is what/how I believe these were selected... After each chassis was assembled initially and designated options selected... GM balanced out each corner of each chassis' variances with a selected spring rate & height to keep the car balanced... remember these were mass produced vehicles with a lot of variances in tolerances.. the Springs also varied in their actual height vs design height... The "computer" was likely a simple calculation based on chassis weight, what spring rate was needed, & a combination of offsets in the actual height of each spring... Again, this was needed to offset the variances in each chassis build, its options, & total weight to keep the car level and tracking evenly...
Each spring was rated and then catagorized by its actual variance in load rating and actual ride height... ie each spring wasn't exactly the same height so it makes sense that springs were grouped together by their rate and further seperated into smaller RPO Coded bins by their actual ride height...
When the calculations aka "Computer Selections" were made, the designated RPO bins were sourced for the correct springs to level out the chassis.
As for the "LJ", yes "L" was for Luxury.... the "J" was for "Model J"... to understand this, you need to know some crucial and some very important pieces of automotive history...
The Model J was originally a model of the infamous Dusenburg... some of the greatest automobiles ever built. Legendary Cars!
Fast forward to 1967, John Z. DeLorean was the Head of the Pontiac Motor Division (PMD). His GTO idea, originally poo-poo'd by GM Brass, now dominated both the streets and pop culture. Pontiac Sales were spectacular, however, one Pontiac in particular, was sinking fast... partially because of the GTO's success and the numerous cars copying its big engine/midsize car concept and the all new Mustang Pony Car. The Grand Prix's other short-coming was that its "Sporty Concept" was outdated because it was a "Sporty" Full-Size car trying to attract younger, upscale buyers in a market over-saturated with lots of full size cars. Worse, the Grand Prix competed against two other Full-Size Pontiacs that shared the same platform... the Bonneville and the
Catalina... John Z. DeLorean, being an true engineer by trade, was also gifted with the talents of organization, negotiation, elbow rubbing, quality control, sales and marketing, & the ability to see what people (the market) wanted and capitalize on it fully.
In 1967, he undertook a huge personal effort to redesign the Grand Prix into a Personal Luxury Performance Car... with several nods to the Dusenburgs, he borrowed the "Model J" nameplate, and some styling cues. He also came up with the "SJ"..."Sport" performance model and the "LJ" "Luxury" model... Hurst joined in with the "SSJ" Hurst Grand Prix...
The 1969 Grand Prix was DeLorean's newest baby... it featured unique Grand Prix-Only door handles, optional real wood dash inlays, wooden shift knob, wooden rim steering wheel, and wooden center console inlays. The car was shrunken down and put onto a stretched A Body Frame... (which became the first G Body). The body featured a short trunk with a 6ft long hood, the longest hood ever used by GM car, at the time, (another Dusenburg detail). A huge Chrome Grille split by the bumper also hinted at styling cues taken from the Dusenburg. The interior was completely designed around the driver, starting with the Driver's door panel putting power controls at the driver's fingertips, blending somewhat into the dash, which wraps around the driver like a fighter cockpit, & sweeps down into the center console. The Passenger Seat was a pretty much relegated to "Guest Status"... Bucket Seats, Center Console, and a Manual Trans were Standard Items... an automatic transmission and bench seat were secondary options. The Standard Engine was the Pontiac 400, with a few potent 400 & a few powerhouse 428 options... John Z. DeLorean saw to it personally that the Grand Prix had the best quality controls of any GM Division, including Cadillac... Sales of the first "Personal Luxury Car" were highly successful... unfortunately, John Z. DeLorean was promoted to head up and boost Chevrolet, which was losing market share. In 1970, the Grand Prix was joined by the all new, Oldsmobile Cutlass Supreme and Chevrolet Monte Carlo... both of which enjoyed their own spectacular sales.. Chrysler and Ford jumped onto the concept and redesigned many of their cars to copy the ideas seen in the Grand Prix.... by 1973, everybody was in on the concept and the era of Macho Machines had begun.
