What have we got?
The car is a Mercedes-Benz
The venue is Indianapolis
The W165 for Caracciola never reached Indianapolis so it must be the W154 that Don Lee ran
The driver is not either of Don Lee's drivers - Duke Naylon (1947) or Chet Miller (1948),
And there the trail runs cold.
After 1948 the car was re-engined so strictly was no longer a Mercedes-Benz but became a Mercedes-Benz based Don Lee Special or similar.
In race condition the 1947 car was signwritten with "Don Lee Special" and a Mobil Pegasus on the scuttle and this signwriting was carried on into 1948.
I have seen photos, but can't find them now, of the car after 1948 when it was more extensively signwritten and I think repainted.
But the car in this photo carries no signwriting.
So I'm totally baffled