[jeffschevelle]

I have seen small bits of the book with the ECL breakdowns, and for some options and some years it actually does identify exactly what models each ECL applies to. For example, 67 Chevelle L78 production (total 612) is shown with two ECL's split between 13817-67 [SS Coupes and SS Convertibles] (578 units) and 13480-680 [Elcamino and Elcamino Custom] (34 units). That's how we knew exactly how many L78 Elc's were built like the one I had at MCACN last year. (Although I screwed up and put 35 on the sign!!)

For the options that have several ECL's listed but do not tell you what each one applied to, understanding why there would be a different ECL code in the first place is the key to deciphering all that data I think. For example, why were there two 67 Chevelle L78 ECL's? Why not one? Why not four? The reason is that (as I understand it) each ECL represents a parts list of every part that had to be added or changed for a given option, OR it can represent a different price for the same option when coupled with other different equipment. With that understanding, it is easy to see why there were two 67 Chevelle L78 ECL's:

To put an L78 in an SS coupe or SS convertible required exactly the same parts, and the option was the same price. All SS's already came standard with 396/325 engines, HD floor shifted 3-spds, 12-bolt rear axles, big block springs, and big fuel lines and sending units. So adding an L78 to EITHER of those cars involved only the engine, carb, air cleaner, fuel pump, DG pulleys, clutch fan, and 4-row radiator. There would be no reason to have a different ECL for an SS convertible L78 because the parts list and price were exactly the same as an SS coupe L78.

But the Elcamino models had to have a different ECL because a lot more had to be changed, and the price was higher. Any 13480 or 13680 V8 Elc came standard with a 283 engine, regular column shifted 3-spd, 10-bolt axle, small block Elc springs, single exhaust with small tailpipe, small fuel lines and sending unit, and a small radiator. So putting an L78 in a V8 Elc involved replacing ALL those parts (along with the carb, air cleaner, fuel pump, DG pulleys and clutch fan), and the engine upgrade cost was to go from 283 to 396/375 (rather than from 396/325 to 396/375). But there would be no difference at all between upgrading a 13480 Elc and upgrading a 13680 Elc; therefore only one ECL was needed for both Elc models.

Then take by contrast an L79 in a 67 Chevelle. That was not available in an SS so any L79 upgrade started from a standard 283 V8 spec car. So you might think there would only be one ECL for an L79. But there actually should be at least 8 different ECL's for that. The variables are:

- Small clutch L79, versus HD clutch L79 (the engine was a different part number for the HD clutch)

- Coupe/Sedan/Wagon 5/16 fuel line (for open frame rail), versus Convertible/Elc 5/16 fuel line (for boxed frame rail).

- Coupe/Sedan/Convertible fuel tank with 5/16 sending unit (the tank and sender were an "assembly" part number in the plant), versus Wagon/Elc fuel tank with 5/16 sending unit.

So, 2 x 2 x 2 = 8 possible combinations of 67 Chevelle L79 parts, depending on body style and clutch. So there should be at least 8 ECL's, for:

1. L79 in a Coupe or Sedan with std clutch
2. L79 in a Coupe or Sedan with HD clutch
3. L79 in a Convertible with std clutch
4. L79 in a Convertible with HD clutch
5. L79 in a Wagon with std clutch
6. L79 in a Wagon with HD clutch
7. L79 in an Elcamino with std clutch
8. L79 in an Elcamino with HD clutch

***
This is all fascinating stuff to me, and I REALLY wish I had a copy of that ECL production book because I am pretty sure I could figure it all out given a little time, and pics of a bunch of original window stickers!!