I have been slowing picking thru my machine shop buddy's race car shop stash, and found some more 69-72 matching number BBC heads. It's kinda fun, like digging for a barn find. But dang are they heavy! All guaranteed rebuildable cores. He can rebuild too if desired. ($400 for std head rebuild.)
One refurbished (Mar) set is already on it's way to Fla for a 70 LS5.
Oval Port Cores $500 & Rectangular port Cores: $1500
These are what I have found so far:
1969 Rect Port 840s C.27.9
1970 Oval Port 290s A.14.70
1970 Rect Port 291s K.28.9 / L.6.9
1972 Oval Port 292s A.4.72
1972 Oval Port 241s A.28.72
Better Pics:
Rectangular Ports: $1500 or BO
840s
https://www.corvetteforum.com/g/album/19804702
291s
https://www.corvetteforum.com/g/album/19804659
Oval Ports: $500
290s
https://www.corvetteforum.com/g/album/19804659
292s
https://www.corvetteforum.com/g/album/19804630
241s
https://www.corvetteforum.com/g/album/19804576
More random date rebuildable heads available for less if desired. Like $100