The 300SD (126) are awesome cars. Good ride, low maintenance, lots of parts available and rock-solid reliable. The 300SDL a little better ride, fewer parts and not as reliable.
I don't know much about the 124 cars.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R