Numbers matching

http://www.forabodiesonly.com/mopar/showthread.php?t=328928
1968 should be back next to the bellhousing
Do you have build sheets for either car? usually found under the back seat. That will give you the sequence number which can be compared to the radiator support and trunk lip. Things got much easier in 1969 but in 1968 at least the high performance engines got the VIN otherwise everything is sequence numbers.
1968 manual transmissions should have the VIN as well on a raised pad on the passenger side.