Says here in my book they are from late 70's and suck ass. Not suppost to be on 351 block. My castings are D5OE-A38, should be off a 71' block. But i got them pretty cheap ($100) and they already had bigger valves 2.02 intake and 1.60 exhaust and were already ported nicely. I'd say i got a hell of a deal.
D80E's should be a 78 or slightly later head. I have a couple sets, including a ported set. Porting improved the performance noticeably. Should have pedastal rockers and cast in smog passages.
They are as good as any other similar sbf head, except that they have the 70 cc large chambers, and need to be milled as much as possible to get any compression at all. I would not put much effort or money in them at this point in time, for performance use.