273 rockers on 340 with hydraulic cam

Will do triple R
You will have great results! Mike is a legend genius! He fixed me up with my unicorn slant 6 head after I put the 318 valves in it. They are .300" longer than the slant 6 valves and required a good bit of correction for the rocker shaft location, so I have first hand experience with Mike's expertise. He's top notch.