C3 headlight assembly differences

[Dennis D.]

Re: C3 headlight assembly differences

The 73-75 part is physically different from the earlier 68-74 version. That is why you must use the spacers for the later support to work in the earlier cars. You have to look closely at the arms on the supports, and if you look at the photos I posted you can see the difference in all three supports. They are all three different, that is why they all three have different part numbers. It is not a situation where they just changed the number on the box, the piece itself is different. When the part changed in 73, it became the only part available for service of the 68-72 cars, with the use of the spacers.
Lynn

Maybe I wasn't clear. I get the 3 different part numbers. 68-72; 73-74; 75 on. There's 4 in Joe's senario. The 4th being the 68-74 SERVICE REPLACEMENT, which I suspected, (and Joe I guess has confirmed), that this is actually the 73-74 piece as a kit which included the spacer block.

So, just for my own info, Lynn... if that GM box in your photo is the support that includes the block/instructions, is the part number on the box 14084417 or 14084418 ? Is the number on the support
331825 or 331826?

[Lynn H.]

Re: C3 headlight assembly differences

Dennis------


The 73-74 supports were never available in SERVICE under their original part numbers, GM #331825 and 331826. Instead, they were the ones supplied under SERVICE-only part numbers GM #6258533 and 6258534. Why? Because these part numbers define, basically, a "kit" which includes the 331825 and 331826 supports PLUS the hardware to adapt them to the 68-72 applications.

When I used the term "functionally interchangeable" with respect to the 1968-72 and 73-74, I did not mean that the 2 pairs were identical. If they were identical, there would not have been a changed part number for 73-74. However, if someone has a 68-72 and needs a new support (or a complete assembly), they can use a support from a 73-74 by also using the shims (easily fabricated). In fact, since late 1973 and until they were discontinued, that's exactly what one would have had to do if they had purchased a NEW support from GM for a 1968-72 (although the shims were included with the SERVICE parts).

I did not get into all of the above in my original responses since the "thrust" of the question was relative to what year headlamp assemblies would work for a 1968. That is what I focused on rather than "correct in every nuance of detail".

Now, one more thing anticipating someone's question: we know that the 73-74 supports can be used for 1968-72 (i.e. rearward compatibility). However,
can a 1968-72 support be used for a 1973-74 (i.e. forward compatibility)? I believe the answer is yes, but they have to be slightly modified. I've never done it, though.

Joe,
I'll buy all that!! Kinda what I was thinking. I have a NOS set of the 533, 534 supports with the instructions and the hardware (shims and screws in the bag), and The way you explained it, is what I was of the belief. That once they changed the support in 73 the earlier one was no longer available after stock was depleted. Like you say, no problem with the 73/74 in the earlier cars. And with the other way around (68/72 in 73/74), like you say can probably be made to work if someone had a mind to. From what I see in 4 aftermarket catalogs I just looked at the reproduction supports offered say 68-74. I have not seen anyone making the 68/72 part in reproduction, but they may be out there. From a value standpoint, I have always got GOOD STEW for the 68/72 support in mint condition (more than what I can buy the repro 73/74 for), so I am not sure I would want to modify one of these for the later cars, given the option.
Lynn

[Lynn H.]

Re: C3 headlight assembly differences

Maybe I wasn't clear. I get the 3 different part numbers. 68-72; 73-74; 75 on. There's 4 in Joe's senario. The 4th being the 68-74 SERVICE REPLACEMENT, which I suspected, (and Joe I guess has confirmed), that this is actually the 73-74 piece as a kit which included the spacer block.

So, just for my own info, Lynn... if that GM box in your photo is the support that includes the block/instructions, is the part number on the box 14084417 or 14084418 ? Is the number on the support
331825 or 331826?

Dennis,
The box in the photos is original and correct, I have a set of 533, 534 part numbers that was purchased new in 1978. I have the set and the boxes are marked with P/N's 6258533 and 6258534, which are the kits that consist of P/N'S 331825 and 331826 with the hardware.
Lynn

[Robert W.]

Re: C3 headlight assembly differences

Thanks so much for the answer guys, I will have to keep looking for the appropriate set for my car.