This is what I used on my 68 4dr hARDTOPI have not been able to find a door weatherstripping kit for a 4 door hardtop 1968 Plymouth Fury.
970481-C 65-68 C-body 4 Door Hardtop- Complete Set+$100.00
DMPS-3564 Cat Whiskers Top Cat??? Correct Side Window Sweep Kits 1965-1978 C-Body - dantesparts.com