Work's been slow, so here's some research I've done on the '68 model year springs. Ya'll who own other models, or who have build sheets, this may not be applicable.

The sources for the research are the '67 & '68 Assembly manual spring charts, and the spring charts from a Chevy parts catalog, dated 8-72.

The '68 AIM shows 5 revisions in the spring charts, beginning August 2, 1967, and the last one listed January 17, 1968. We have no idea whether the revisions were design changes or part number/letter code changes.

I've found is that the code letters in the parts catalog cannot be relied upon to be correct. For example, rear spring part # 3893389 is coded BJ in the parts catalog, BU in the AIM, ; BJ code in the AIM is part #3893392 and that number is BT code in the parts catalog.
The parts catalog has charts with the model, body style, and options that are used to pick the proper spring for the cars by a code letter. As many as 5 letter codes changed to just one part number, probably as an inventory control measure. Example-rear spring codes BK, BO, BP, BZ, and CA are all part #3893397 according to the parts book. The BP letter code and #3893397 is listed in the '67 AIM for a SS396, but that letter and number isn't in the '68 AIM anywhere. The BK code is shown in the '68 AIM as part #3893394.:confused:

So, if the letter and/or part number on your spring tag doesn't match up with the AIM or parts catalog, I wouldn't get too worried about it. If you're lucky enough to have a build sheet, then the letters in box 13 are the front spring codes, box 14 has the rears.

I've made a list of front and rear springs by part number and letter code for '68's from the AIM and catalog, but NOT by application. If you need to know that, buy an assembly manual.:) Rather than take up Al's space, if you want the list, PM me with your email & I'll send one out to you.

BillL

Put me on the list Bill....

Dave

I have recently experienced this in a previous post where my front spring broadcast code supposedly wasn't used for 1969 according to the Chevy Parts Manual. In the end, luckily someone else's build sheet from 1969 helped to solve the mystery and showed my broadcast code as being used.

GM still does this today, at least with shock absorbers. They will release a plethora of dampers at the assembly plant, but only make available a few as service replacements. I believe this is done for a number of reasons, one is for saving shelf space at dealerships.

By the way, I work at GM, and pulled the drawing for the 1969 and 1970 front springs. It doesn't show the broadcast code (they were all removed in the last revision of the drawing), but it does show the rates, capacities, loads, etc. If you own a '69-'70 vehicle and need to know the spring specifications of a certain part number spring, I can help you out. Just send me a PM.

Thanks for the post.

Mike