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I found a block for my 68 with following details :
321 4 bolt block with T1120ID stamped, no vin. The cast date I believe is an I7 but the cast date is fairly unreadable.
My car's build date is C 05 = Oct 05 , 1967
I can't work out the stamped suffix number on this block. No ID in my black book for 68.
Also if the block has a casting date of I...7 , being Sept 67 , shouldn't the suffix stamp be something like T09...I. ?
The "ID" suffix was used for the 427/425hp engine in '66-'68 full-size passenger cars. Pretty unusual for a block to sit around at Tonawanda for two months before being machined/assembled. If there's no VIN derivative on the pad, it's either a service engine or it's been decked and re-stamped; does the pad show longitudinal broach marks?
My Chevrolet V-8 Engine Code Pocket Guide shows:
T -- Tonawanda (NY) plant code
11 -- Month of production (November)
20 -- Day of month (20th)
ID -- Engine Suffix generic for 66-68 427