I do not know how many exist (I am guessing less than 5) but if you want a non-Duesenberg with a Duesenberg engine look for a ReVere. ReVere is another of the gems of Indiana. Made in Logansport, Indiana the ReVere used a 4 cylinder Duesenberg racing engine for a while to power them. Just don't expect to find much support in maintaining one. The ReVere is one of the makes that are targeted for the Auburn Cord Duesenberg Automobile Museum to acquire.

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Current:
1985 300D aka Miss Margaret
1991 300SE aka Alarice
1995 SL320 aka Samantha
1997 K1500 Silverado
Past:
1999 E300 ex-wife got it and let her son ruin it
1984 190 2.3 ex-wife got it and let her son destroy a great car
1985 300D (CA version) aka Maybelline lost to deer at high speed.
1981 300D aka Madeline (went to salvage at near 400k) rusty, yet best car I ever drove
Wishlist:
McFarlan TV6 (only a few privately owned)
ReVere with Rochester engine
1917 Premier (only one left)