The difference between a solid lifter and a hydraulic engine is in the oil passageways in the block, not the cylinder head. There will be a large-diameter hole drilled from front to back through all the lifter bores on the hydraulic-lifter block to supply them with enough oil to keep the plungers pumped up. Trying to drill a non-hydraulic block accurately is almost impossible, so if your block isn't a factory-drilled one you'll need to find another block. I believe the 1958-62 blocks were all drilled for hydraulics whether or not they came from the factory with solids.
The hydraulic-lifter camshaft will have a different lobe profile, so you'll need to purchase a new, not used hydraulic cam and new lifters to match it. Once a cam and lifters are run together, never swap lifter positions, or try to match up used parts from diffrent engines. They will wear out almost immediately due to wear patterns not matching.
Jerry
