The history of some German racing Bugattis is difficult to trace, because they had been seldomly used in the 2nd part of the 30's, and if only in secondary or only local events. Therefore I do not have much about Herbert Wimmer. The interesting thing is that in 1933 he is listed with a T51 instead of T35B, incl. the Nürburgring Eifelrennen. Possibly he mounted a DOHC engine in the car, but this is pure speculation.
When after the war in Germany racing started again, despite chaos, destruction, hunger, and shortage of almost everything, some hard headed souls pulled out of sheds, cellars, and other hiding places everything which looked raceable, including some ancient Bugattis. The very first postwar race was the Ruhestein hillclimb on 21 June 1946, held near Reutlingen in the French Zone in southwest Germany.
First in the racing car class was Fritz Georg Martin (other sources say Hansgeorg Martin) from Rottweil in the old Burggaller monoposto #51134:
(source Stadtarchiv Reutlingen)
Martin later entered this car at the Dreiecksrennen Karlsruhe (29 Sep 1946), then he disappeared.
Possibly #51134 went to Fritz Gerster, but that is unclear. His car is only described as "ex Steinweg Bugatti", but before his fatal accident in 1935 Rudolf Steinweg did not only own #51134 but also the ex-Kappler ex-Prinz zu Leiningen T35C.
Also present at the Ruhestein was Egon Brütsch with a car I believe was von J. von Morgen's T51 #51139. There is a press report from 1949 in "Motorsport + Motorradwelt" that Brütsch's ESB Special is based on the von Morgen Bugatti.
Without doubt a T51 engine, and there had been not so much around in Germany.
Another starter at the 1946 Ruhestein hillclimb was Heinrich Herbster from Lörrach, reportedly in a T35B:
(source Stadtarchiv Reutlingen)
Herbster raced this car also at the 1947 Maipokalrennen at Hockenheim, where it was reported as T51. In 1948 he was the very first customer for the new Veritas F2 monoposto, but because the engine was not ready yet they put for the Eggberg hill climb Herbster's Bugatti engine in it:
Later this was removed again and the standard engine was installed. Clearly a SOHC engine, no T51 DOHC.
This all happened within a limited area of southwest Germany. The Eggberg and Ruhestein hills and also the Hockenheim circuit are located in the area, as well as the drivers Wimmer, Martin, Brütsch, Herbster, and Gerster. Wimmer was no active driver anymore, but he was still present on the scene. There's a photo showing him standing around at the 1948 Eggberg HC together with Hummel, Gerster, and Troeltsch (Ernst Troeltsch owned the Burggaller monoposto after Steinweg's death before he sold it to Leonard Joa). Therefore it could well be that the Herbster Bugatti in fact was #4948 which he bought from Wimmer. Remarkably Wimmer and also Herbster in the entry lists vary between T35B and T51, which may be a hint that their car was a T35B converted to T51. I will not exclude that the original engine went with the car, and was then used for Herbster's Veritas, but this is pure speculation. It is reported that at the Eggberg 1948 Herbster's Veritas-Bugatti was not running well, and it had been rapaired at Gerster's nearby workshop (he called it "Polyclinic for race and sports cars"). It seems that Gerster was a kind of regional Bugatti specialist, so it would make sense that he took over also #51134 from Martin. And also the Herbster car may have found his final home at Gerster's premises. But again, all highly speculative. And even more speculative would be that the monoposto body of #51134 was fitted by Gerster to the Herbster car...!
However, all these speculations invite further research. Any contributions...?
By the way, David, I have some photos of #4948 with Pietsch in 1932. Any interest?