.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports... as for the block your lookin at either a 2 or 4 bolt for that year... seriously i typed chevy casting numbers and got that info in 30 seconds the intraweb is our friend.
those heads are the best stock oval ports and can support 500hp with very little work
Stock power is somewhere around 250 but with a pair of headers, intake, and cam swap you can get close to 400