Ulf,
I have a Comp Cam #20-246-4 in my 273. Works perfect with Edelbrock D4B intake manifold and Edelbrock 1406 (600 cfm) carb. Added to that Spitfire headers and domed pistons. I will follow your build /restoration with great interest.
I've never heard of Spitfire headers until this morning!! A close friend of mine offered a set for an early A-body. Not sure the Doug headers I have fit my car. Might be 67 and up!:banghead: