I thought it may be of interest to publish the whole story about De Tomaso F1 #003 to avoid confusion with other De Tomaso F1 puzzles that possibly may come up in the future:
1) Image (taken in the beginnings of the 2000s) of the Alfa Romeo engine, De Tomaso Alfa Romeo F1, #003, 1961, without double ignition
2) Article: Conrero, Alfa Romeo, 1961 (sorry French text). Engine pictures of Gino Munarons Cooper T51 Alfa Romeo Conrero 1961
3) Another picture, Vaccarella, Italian GP 1961, De Tomaso Alfa Romeo #003. It was Vaccarellas F1-debut and Wolfgang Berghe von Trips' last race
4) Racing history and specifications of chassis #003