1965 Valiant 200 convertible (minor project)

You've definitely got the peanut heads, which are 75 and newer. More specifically, a bit of online research says the head's casting number on the head indicates 1979-1980.

According to one online source, the block casting number indicates a so-called "30" block, used for the last iteration of forged crank motors. But forged cranks were phased out at the end of 1976 (part way through the 77 model year). And forged crank blocks and cast crank blocks are not the same, and their cranks are not interchangeable, so if the foregoing is true, the 79-80 head is not original to the block. ??

Heads are interchangeable, though, regardless of solid or hydraulic lifters, or forged or cast cranks. So long as you run the valve gear (pushrods, rockers) for the kind of cam you have.

I think the foregoing is correct, but, as always, I'm happy to be corrected by someone who knows more than I do. Particularly in regards to the meaning of the block casting number.