Late 70s through mid 80s had the coffin boxes - by 87 the coffins were gone. The 20, 22, and 24 foot models had different coffins, each getting bigger with the boat. I've always felt a 24 foot CCP with the 22 foot coffin would be a good match, because it would give an extra open space at the bow.
I like the 22 foot coffin a little better than the 20 foot model, because it has the extra box in the front that opens forward, with a lockable hasp. There was also an optional under-deck locker offered in all CCP models - just in front of the coffin.
The coffins were replaced by in-deck fish/stowage boxes, but I like the coffins for seating and dry stowage. I can seat 6 on my boat comfortably using the coffin for seating. The coffins are also insulated so you can use them as big coolers if ya want.
Not a great picture here, but you can see the coffin layout; note the under-deck access hatch in front of the coffin:
Hope this helps - see ya on the water!