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Discussion Starter #1 (Edited)
I have searched the internet over and over and have YET to come up with what I thought was undeniable proof of matching numbers on a 68 GTO.

Bottom line - is the 6 digits stamped next to the timing chain cover on the machined surface supposed to match the last 6 digits on the VIN?

I have thought for years that my engine - 400 4bl 9790071 - was merely a swap since the last 6 digits do NOT match each other.

Yet, of late, I continue to read about "period" matching - mine would appear to qualify for THAT, and I have NEVER seen pics of stamped #s on a block that DO actually match the last 6 of a VIN - either under the windshield or on a title - even though many claim to be "numbers matching"...

Do I have to buy the PHS ppwk to see what matches or is the fact that my numbers are different prove it is a swap?

Tired of searching for pics of proof positive matching numbers...

And sorry if this is covered elsewhere in this forum, I have searched here for so long I can't see straight, and again have not come across definitive proof of any car that DOES have identical 6 digits.:crazy:
 

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Yes, this has been covered many times in the General Discussion forum. Place your question there for a better response, but I will try to help out here.

I am not sure if the number you see is related to the vin or not. I am thinking that the number is the engine build sequence number, but not 100% sure. Pontiac did match the engine number with the vin, but not sure what year they began doing this.

The 2 digit letter codes for 1968 GTO are XM, WT, YS, WS, YZ, & for Ram Air engines XS, XP, WY, XW.

Heads for the 1968 GTO are found on the center exhaust port. Should be #16.

The factory 1968 cast iron Q-jet intake will be part #979140 or the 1968 1/2 #9794234.

To date code your block as being 1968, look at the back of the engine near the distributor for the block production number. The first letter is the month (A=Jan., B=Feb, C=March etc.), the second/third number is the day, the last number is the year -so it should most likely be an "8". New model production begins in August of the preceding year. So your block could have a "7" as the last digit if it was made in Aug=H,Sept=I,Oct=J etc. which makes it an early production model.

If the block is a late 1969 or later block, it has the cubic inch size cast on it between the first freeze plug on the side of the block. The 1968 block should not have the cubic inch size on the block.

Do you know the engine to be a 400CI? Royal Pontiac in Michigan did install a factory blueprinted 428CI in 1968. The 428 can be identified by a large raised almost pyramid shaped lug at the back of the block on the right side of the distributor.

That might help some. PHS documents would be the way to go as they give many details of your cars build and options from the factory. And, post your question again in the General Discussion and you will get a few more responses.
 

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Discussion Starter #3
Thanks for ALL that.
I have a long list of numbers for everything from the tranny to block, intake, heads, rear end timing chain cover etc. Dates, and even TIMES. 400 CIs.
It's just that my stamped block # and title # do NOT exactly match.

As I mentioned, if it's a block swap, someone replaced it with another from the same year, and I'm guessing used all the original bolt on parts. A good effort if it had to happen...

Just read a lot lately about "period" correct and having never actually SEEN 2 numbers match exactly on a GTO started wondering why.

Read somewhere recently as well that Pontiacs were not even stamped with a serial # on the machined face until somewhere in 67.

Lot of info and MISinfo in the Internet world, and even saw one today showing the block stamp and the Title - numbers clearly did NOT match but listed as a #s MATCHING GTO.

Just been trying to get to the bottom of it with what SHOULD be a very simple question.

Thx again.
 

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The VIN stamping on the engine can be very faint, you will need a flashlight and a wire brush. Here is a pic of the location. If you want to see a block that matches the VIN, come to Columbus OH and I will show you mine. Go to Wallace Racing website for all kinds of Pontiac info.
 

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So rlslavik, it sounds like you have come to grips with the "period correct" thing. Now, what is the serial number on your block? Matt
 

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Discussion Starter #6
My machine stamp ends in 256.
My VIN ends in 309.

Yeah, as I think I mentioned, I never thought of this car as "numbers matching" from the first time I ran through the numbers some 20 years ago.

Doing a restore job as we speak and started reading more and more about "period correct" and figured mine was pretty much THAT.

Then I simply realized that I had NEVER seen pics of A VIN and machine stamp that matched on a GTO, continued to see more about period matching, read where the machined numbers weren't even DONE until 67+, and even saw a car ( on the internet) that was for sale as NUMBERS MATCHING when the actual PICS showed numbers that did NOT match.

???

Started feeling a bit confused so I decided to bring it out in the open and ask any/all that cared to share.

And for those interested, one person did PM me pics of matching numbers on a 68 GTO - both the machine stamp and the PHS doc.

They DO exist...

Knowing all this merely helps to determine how far I care to go with my rebuild.
$$$
I'll be happy with a straight black primer daily driver that runs like a raped ape.
 
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