There has been talk of taking a N/A block and tapping into the oil galley to add piston squirters. Could this idea be applied to a solid lifter head, tapping into an oil galley so hydraulic lifters could be added?
Also, why is the cam cap #4 missing on hydraulic heads? Is that for an oil-pressure relief valve to avoid overpressurizing the lifters?
Enough time & money you can do about anything. Major problem is valves & springs are different length, so changing lifters alone woudn't work. With current availability of parts doubt it would be worth cost & effort. Pretty sure heads missing #4 cam cap (unless hosed up by PO) s/b for 8V gassers. Regards