Bill Weertman [[the head of Chrysler's engine design department during the development of the 1964-71 Hemi, and many others) has written the last word in books on Chrysler power plants

http://books.sae.org/book-r-365

You may find it at the Skillman branch, it's pricey, but priceless if you value this information.
You can contact Chrysler for vin # look-up service for that year, they have mircofilm records of cars and trucks 1930-1967, and then later years, I think they have 1988. The crucial years of the [[highly valuable) muscle cars microfilm has been lost for years, gone. An individual has made a name for himself "suthenticating" those muscle cars, all he has to go on are factory part supersession letters that might state "all 1968 Dodge Charger models After vin# XXXXXXXXXX, use part # YYYYYYYY in place of part #ZZZZZZZZZ, and he has extrapolated the "information" from there.
Those are both excellent engines, mated to one of the very best automatic transmissions ever made, put into one of the most substandard bodies and electrical systems made this side of England. Parts are readily available for the engines and trans, trim parts and correct interior materials will be the big challenge.
You are looking for an M body, actually, they are pretty good, probably one of the best Chrysler made. Around here you either see them in cherry shape or absolute beater, but still going.