Though I'd post some pix of the early and late head

Late head with perf springs installed


Late head - ported with OEM exhaust gasket installed. Close up.



Stock early head with late OEM exhaust gasket installed



Stock early head top - ported late head bottom - exhaust ports


Stock early head top - ported late head bottom intake ports


Late head with inconel valves installed - turbo ready


51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them