yeah no chance in hell you could consider putting a dohc engine's head on a pushrod motor its like puting a square block in a circle hole, it cannot be done.
and i agree with the above cracking a head isnt too common i dont think and its hard to doand very rare with an iron head, if your having coolant leaking and power loss i'd check the head gaskets
heads really only have warping problems and thats more on the alum head side, alum heads can warp easier , but iron heads are pretty durable and its hard to destroy them