yes, the mural was there in the late 1970's, not 1968. And it was there throughout the 80's.
As for Jack Schlein, good chance that name is Jewish, but could have been German. But back when that photo was taken, the majority of people in Bergen County were of white Protestant background, and it was considered unacceptable to be Catholic or Jewish (and to be Black was even worse). There were riots and demonstrations and marches against Catholics in the 1920's and 1930's. This part of our history is not well recorded. There was sheer hysteria in Maywood when Queen of Peace began construction. There was a full-scale riot in Teaneck when a Catholic family rented an apartment above a fire station. History records the discrimination against Blacks, but not against Catholics and Jews.
And of the population of Bergen County which was NOT of white Protestant background, many were working class people who couldn't afford to buy a car. To be a car dealer at that time meant dealing with the racist buyers. So from a business perspective, as sad it is sounds, a Jewish businessperson might want to appeal to the racist Klan mentality by dressing up in that fashion, just to attract buyers. Truly pathetic if he was German, and even worse if he was Jewish