The credit thing and the car in lake description matches "The Junkman":
http://www.imcdb.org/movie.php?id=84184
The car with gullwing doors:
http://www.imcdb.org/vehicle_7478-Bricklin-SV-1-1974.html
Kind of things seen in credits (ending, but maybe same in opening):
http://www.imcdb.org/vehicle_16426-Iso-Fidia-1969.html
http://www.imcdb.org/vehicle_7507-Lotus-Esprit-Type-79-1975.html
There was quite possibly something with a horse used after a crash, but there were so many crashes in that movie that I do not rememeber exactly