I have found chassis numbers in a variety of places.
Most common for series 2a is RHD drivers side dumb iron just above where the spring mounts are welded to the box chassis, almost always on the outside edge.
However, I have also found them on the left chassis section under the engine mount on the inside and on the inside face of the left dumb iron.
My current landy has none of these but the dumb irons have obviously been replaced.
The identity plate is on the inside though (beside the steering column on the inside of the bulkhead) but this has also been replaced.
I had to do some research though as my chassis no is for a 88in soft top but my landy is a 109 hardtop, if you believe the chassis coding and I suspected a ringer.
However, I have the original sales documents and registration documents from 1968 when it was exported to Islamabad and when it returned in 1974 all show the chassis no and state the vehicle as a 109. Hard top was added in Islamabad and the 1968 number plate was added when it returned in 1974 after an identity check by the dealer at the time.
It would seem that Solihull were not that consistent with their stamps, especially on exports.