I'd dropping in a fresh 235 or 261 and be done...you could have him back on the road in one weekend. The 6-cylinder engines are good engines and have given countless millions of miles of service for decades.
Swapping in a V8 will have gas and clutch linkage issues to work out as well as radiator and exhaust fitment issues...this all takes time to research and figure out.
My .02 cents,
Mike B
