Sorry, can't find a listing for those heads 283 or otherwise. I did, however, find that block number...afraid it doesn't appear to be anything special. It shows for anything from '58-'67 283 for passenger car or truck. Because there's a seperate listing (different #) for 327s of the same vintage, I'm gonna GUESS it's just a plain ol' 283, not one of those cool blocks that came from the factory clearanced for either a 283 or 327 crank. Again, sorry that's all I got, and my best assessment. I'm sure there's someone out there with some better information available.
'69 Garnet Red Convertible, Ivory over black, 350 w/turbo 400