Hello John,Hello John.
The Zagato build number would be welcomed for any of these cars. The easiest place to find it on an unmolested car is stamped in the centers of the covers behind the headlamps, easily visble with the nose tilted up. Because it is possible that parts were mixed early in the lives of some cars, it is always nice to find the number in more than one location on any car. Numbers can be stamped, scratched or even finger painted in undercoating.
John de Boer
The Italian Car Registry
Hello Richard,Chassis tubes may be flattened somewhat at joints but they are not oval.
Besides, other parts of the car are lower such as the sump and some suspension ends, etc., etc.
(And, on top, the motor is canted as much as it is to provide a straight header exit between chassis tubes, not to lower the hood line.)
Chiti was much more pleased with the TZ2 (whose tubes I know nothing about!).