I'm going to edit this post quite often unless other people I.D. some vehicles:

#2: 1973-76 Plymouth Duster
#3: 1969 Dodge Coronet.
#4: 1968-72 Chevrolet Nova.
#5: Unless this is for the moped, I'd say there's a Lincoln Continental Mark III in the background.
#6: 1968-70 Ford Country Squire.
#7: Triumph of some kind.
#11: Late-1960's Plymouth Valiant.
#12: Studebaker Hawk or Golden Hawk.
#13: 1975 Cadillac Seville, which already exists.
#14: Inernational Harvester Loadstar.
#18: 1973 or later Chevrolet Monte Carlo.
#19: 1968-72 Buick Skylark.
#20: 1974 Chevrolet Caprice or 1975 Chevrolet Impala(or maybe Bel Air).
#21: Volkswagen Squareback.
#22: 1970 or later Chevrolet Camaro or Pontiac Firebird.
#25: 1969 or 1970 full-size Cadillac.
#26: 1968 Chevrolet Impala Sport Coupe or Caprice.
#28: 1975 Plymouth Fury, which also already exists.
#29: Ford Ranchero.
#30: Toyota Corolla.
#32: 1973-74 GMC pickup.
#34: First Generation Chevrolet Camaro.
#40: 1974 Chevrolet Vega, which already exists.
#42: 1970-72 Ford Maverick.
#48: This must be the 1975-76 Cadillac Coupe De Ville that Stampede1975 said he saw.
#49: 1974 or later Ford Mustang II.