Frame ID Numbers- How Do I Decode?

I just picked up a frame for a project of mine and need to find out the exact year, so I can buy the correct parts. Its suppose to be a 73-87 chevy 1/2t frame, and the guy thinks that it is a 76, but not 100% sure. I know that these years aren't H.A.M.B. friendly, but this is the only place I know to ask. I only have three different numbers:

T8S517353- found this # on top frame rail, pass side, where the cab sits.

7S483- found this one on the pass side frame horn, outside frame rail.

7802644- found on gearbox, probably not much help.

If anyone can send me to a website that has this information, that would be very helpful. I have been searching for one the past week and cannot find anything. The local Chevy dealer wasnt much help either (go figure). Thanks again, DOOCE

 

I would give it a wild guess as behing a GMC truck from 1978, built in St Louis.

at least that's what I would guess if I saw that T8S.... number sequence on an engine block.

 

thanks squirrel, I tried decoding the same number as if it was the vin, and thats what I came out with, but the numbers are not in the same place as they would be in the vin. It shows that there should be 4 other numbers between the T and the 8.

Is there any more numbers that I may of missed somewhere that mght be of more help?

 

they used a similar "partial VIN" on engines, it gives only the carline, year, and plant, plus the 6 number serial sequence.