2: Mercur Ego 4/14 PS goes with 6: Merkur XR 4 Ti
D: AMC/Armbruster Ambassador Limousine goes with 11: Parikh Ambylimo, as both are stretched Ambassadors
I: Bobby Allison goes with 3: Allison V1710-F aero engine
H: Austin Ant goes with 12: The Ant and the Aardvark
O: Chrysler 72 goes with G: '72 Buick Riviera
9: Sunbeam Harrington Le Mans goes with O: Chrysler 72, 1928 Le Mans participant
And as this is a silly puzzle:
J: Liz Taylor (with Nicky Hilton) goes with car #17, as both were subject of a nose job