Re: 1968 302 sbc
Glenn I believe YW was used in 1966 truck applications as a 327ci 185hp. However that is a 68 block casting number, don't think it was used in 66. Sure it's not YV? Can you find a block casting date at the rear, by the bellhousing mounting flange near the distributor hole? That should confirm when it was cast. But it appears you've been misled, at least insofar as the block was not originally assembled as a '68 302.
1969 04A Van Nuys-built Z/28. Cortez Silver with dark blue interior and VE3. Sold Clippinger Chevrolet. Raced at Lions in LA.