340 w/360 heads, 6 pack & air cleaner help

Get the casting number, and that will tell us more. But they are all about the same. I would guess that since you say it is a 73 340 it is probably a cast crank, low compression, 1.88/1.60 valve setup. That's the way a 73 engine would come from the factory. Who knows what's happened to it in 35 years, though?