Hello Darren,
I've just joined the forum after being contacted by some other members (Thanks Rob and Chris) and hope I might be able to be of some help in sorting out your 1970. I own a few unusual cars (see
www.67fso.com and
www.airl88.com Dec 2002 Vette Vues and Fall 2002 NCRS Corvette Restorer) and have been through what you are going through right now when I first got into this. I don’t claim to be any kind of authority, so take my experiences for what they are worth
The first thing I learned is to move very slowly on altering or doing anything physically to the car until its true identity and history has been thoroughly documented. If indeed it turns out that you have a rare car, it will be a piece of history that you will want to preserve for your own enjoyment, as well as the entire community. This is really fun stuff when you have a unique and desirable car.
The next thing is to seek the advice and expert eyes of those who are very familiar with 68 to 72’s, especially a 1970 in your case. There are very knowledgeable people in your neck of the woods, and I’m sure a few would be willing to help you go over the car in minute detail if you wanted. I could help you get in touch with some NCRS members if you’d like.
I’ve read your previous posts a few times and have tried to sum up the details you have given so far. It sounds like the car has been in your family since it was new, that it is a low mileage car at 21K, and that you might have a significant amount of paper work on it. If you have the Protect-O-Plate with the warranty book, that would be a big help, along with any other sales or delivery documentation. If there is even a small shred of the tank sticker left with any numbers on it, that would be a big help also. Obviously the window sticker is important, but it would correlate the information with the Protect-O and tank sticker.
From your description the car sounds like it might be in survivor condition with original paint, but may have had less than perfect storage conditions over the years. It also sounds like you might have started to partially take the motor apart. I don’t know if you have pulled the gas tank to see the tank sticker or looked in from the gas lid. Sometimes the sticker can look pretty bad from a gas lid view, but isn’t hideous when you actually get the tank out of the car. If you don’t have anything taken apart yet, leave it together! A survivor condition, desirable, one of a kind car is the Holy Grail.
There are a few things you can look at right a way to see if it might be a factory delivered LS6. As you have seen, the stamp pad numbers tell a lot, as does the block casting number 3963512. Find the block casting date, which is on the rear of the block on the passenger side, opposite the casting number. It is possible that the casting date is down in front of the starter for an early 512 casting, but it should be on the rear bellhousing flange by the time yours was cast.
See if the cylinder heads are aluminum or cast iron, and write down their casting numbers and casting dates if you have the valve covers off. If the intake is off, get the casting date and number. Same with the distributor, which is on the neckband, and the coil. Get the carb numbers off the front of the airhorn, starter numbers off the body, water pump numbers under the pulleys, etc. Also take note of what the numbers and letters are on your trim tag, which is in the drivers side door jam.
There are more items that would point to it being an original LS6 with the brakes, suspension, transmission, rear diff, etc., but this stuff can be pretty subtle if you haven’t seen it before. The above items will get you started and at least let you know if it is possibly a factory LS6 or has dealer installed items from later on. During this era it was common for dealers to swap things around as seen fit, so in cases like your car, documentation and close physical examination are everything.
Special cars were built for certain people and for different reasons. Chevrolet was capable of doing some odd stuff, so any tidbits you come up with would help as far as the people who were involved and who they knew.
Hope this helps.
Bob