The casting number is unfortunately on the bottom side of the head and would require removal of the intake to see..There is a date code on the top side though..Look in between the pushrods ...It should look something like this 7h15....The first number is the year of the decade and the letter is the month,followed by the day of the month the heads were cast..We can pretty well figure out the decade just by visual clues on the heads like what type of rockers,the size of spark plugs etc...

 

The D should have been the first clue since 289s were not produced in the 70s IIRC.
And if they are 289 heads, they don't flow very well regardless of the CR in this combo.
I would be curious about the cam also...

 

HAHA... good point!

How could I find out about the cam? The only way I know is to pull it and look. But being as it is still a 2bbl, I might just have a slight misfire somewhere. Wishful thinking I guess!

GT-40 heads would be a good choice for me, no? I should get them milled down a bit to accommodate the taller deck height of my particular block, right?

 

I suppose you could measure the cam lift with the valve covers off, but that's about it.

 

Good idea, but I would need a micrometer for that! F*ck it. When I get a 351 its gone anyway!