Rajo and Frontenac made OHV heads, not sure about any DOHC conversions. Really, it would be fairly simple to adapt a belt drive setup to the front of the engine- - - -just sprockets, idlers, a tensioner, and a belt. No worries about the mesh of the crankshaft and cam gears, etc. That would make line boring the block for insert main bearings a simpler process, as well. I'm looking at a 2.4 Liter PT Cruiser head as a possible donor.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!