The intake would be correct for a CNR 350 300HP engine from a B-Body.
3965577 1970, 350, 4bbl iron Qjet, B F X, 300HP or 350HP.
A280 = January 28, 1970.
3970010 = 1969-1980, 350, 2 bolt or 4 bolt. The higher output CNR stamping probably means it's a 4 bolt main but you won't really know til you pull the pan off.
On the clock dial thing...
From Nasty Z28: "
On some Saginaw blocks, intakes and exhausts a "clock" was cast into the block. The clock is a circle of 10 dots, one dot for each hour of a shift (usually 10 hour shifts). An arrow points to the beginning of the shift an another dot outside the circle indicates what time of day the cast part was made."
The P overstamp is a weird one. I bet there's a story behind that one. I'd be interested to know what heads are on it and what cam and pistons were used.
If you can get a look at the end of the heads behind the accessories or with a mirror on the firewall end you'll see Casting ID or Casting Mark along the bottom edge against the block.
http://www.crankshaftcoalition.com/wiki/SBC_cylinder_head_identification