Tiger -
What you have is a bit of a mystery, but this may help:

3956618 casting was used in 1969 302 engines listed as 290 horsepower, 4 bolt from a Z28. If this is truly what you have it's a gem. However, this casting number is inconsistent with the number stamped on the pad, i.e., the TO625 indicates the engine was made in Tonawanda(T) June(06) 25(25)th.
"HD" is 1965-66 327 and 1969 350

This casting number is also used for:

1969 327 listed as 235 horsepower, 2 bolt main in full size (Impala, Biscayne) and 1969 350 listed as 250 to 350 (depending on how equipped) with either 2 or 4 bolt mains. My guess is that you have a 1969 350. If it's a four bolt, it's a great block to build. If it's a two bolt main - it's like a gizillion other 350s out there.

3932441 are 1969-72 heads with small (1.9, 1.5) valves. If these are the original heads, you probably have a fairly common 250 horse 350.

Regards,
Glenn

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