Ive Been looking at a 64,owner says nos. match. 0413RE.-117377,2870 block,these are ok,heres the kicker,build date I-6-3, owner says its a late 63 block in a early 64?????? is this possible? thanks all.

 

Numbers aren't quite making sense, but it's late, so perhaps I haven't got my thinking cap on straight.

Casting number is OK for 62 to 64 Corvettes.

Assuming what you called a "build date" is really a casting date from the rear of the block, it was cast Sept 6, 1963 and probably would have been used in a '64 Corvette; but, the assembly date for the engine is April 13th (it's unlikely the bare block would sit that long before the engine was assembled), born as a 365hp Holley-equipped with manual transmission, and the vehicle birthday is around May 8th of '64, hardly an "early 64".

Engine casting date and assembly date are normally quite close to one another (often only a day or two), and the engine assembly date is usually well within 6 months of the vehicle build date (often within a week or two). Seven months separation for both stretches credibility.

Not impossible... maybe, but highly unlikely; more likely a restamp with the casting date left original.

I assume you verified the body tag build date shows a '64 body built in April or the first couple of days in May, and that the body VIN tag matches the engine stamp. There's also a VIN stamped on the top of the frame rail above/near area of the driver-side rear upper shock mount.