Here's a proposed overall line-up (minus trucks). It provides zero overlap between Mercury & Lincoln.
FWD/AWD:   Ford	            Mercury             Lincoln                     wlb      ovl
B        F2/crossover      -                   -                           95-100  160-170
C1       Focus/crossover   M3 4d dual*/2d cc   -                            103+     175
CD3      Fusion/Fairlane   Milan*/wagon        LZc(2d zephyr coupe/cc)/xuv  108-     185
D2       500/Freestyle	   Montego(*?)/wagon   LTc(2d towncoupe/cc)/xuv     112+     195
D3(v8)   500Galaxie        -                   LTs(4d townsedan)/xuv?       116      205

RWD:
swb-     -                 -                   2seat-cc                    89-100    180
swb      Mustang           -                   -                            107      187
swb+     Falcon '4'd       Cougar 2d dual*/cc  -                            110      190
lwb-     Thunderbird '4'd  M-CLS 4d*           Mark-X (2d coupe/cc)         115    195-200
lwb      CV#(taxicop)      Marquis             -                            117.5    206
lwb+     -                 -                   Mark-Xs (4d sedan)           120      209
lwb++    -                 -                   Continental (xl '4'd sedan)  122.5    212

* dual= sedan-hatch: sedan look with dual rear opening, full-hatch + small trunk panel
# CV  = CommericalVehicle no retail version
cc    = coupe-cabrio hardtop convertible
'4'd  = suicide rear doors (RX8/Conti'60s-style)
2seat-cc Lincoln = Miata/RX7 OR Mustang based (v6,v8s,v10)
Mark's & Continental share styling and as many body panels as possible (v8s, Continental=v10)
back to 1st rant

Mercury 'M4'