John can you tell if there could be sufficient clearance with a little less cam lift? Have to think that these heads are not necessarily targeted to those who would be running a cam profile with .4"-up lobe lift.
The cam in my iron-head 416" is a .595" lift SFT (achieved with 1.6 rockers) with 5/16" pushrods. IIRC the lobe lift is around .37xx" Might be tight but not like the pics you posted. Presumably roller lifters could be worse since they can be taller. Don't think you'd want to open up those holes too much more towards the outside of the valve cover rail either.
I think most would agree that anything beyond .65"-up cam lift is at the top of solid flat tappet cam range and pretty much into roller cam territory. Are the TF heads a good match for a roller cam/.375" pushrod combo? No idea but seems like they would need some work to get there.
