Hi Sherman,
At the start of small mouth TR3 production, the factory still used the low port head up to engine TS9349E, but with interim enlarged ports to suit the new 1.75" carbies. This was not the Le Mans head.
Engine TS9350E was the first fitted with the Le Mans head, which was a new design, although still low port, but based on the higher output LM heads the factory had developed for the TR2 competition cars. These heads now had the ports properly matched to the 1.75" carbies, and the improved breathing required new TE needles to be fitted to the carbies. Seeing the engine in car TS9100LO would be after TS9350E, if it still has the original head, the PO has described it correctly.
I can't recall seeing any visual difference between these types to identify them externally, and unfortunately I don't have the casting numbers, as my Stanpart component listing book is loaned out.
Regards,
Viv.