Jason,

That is great news that you have an old manx as well. The early cars with the flat strap frames were built in 65 and early 66....look early on in this thread.The flat strap frames were hand built prior to an extrusion die being made for what is current production. I think that the general consensus is that the first 40-50 cars had the strap windshield frame. The first 100 or so cars did not have badges or ID tags.
Additionally, the rear license area was squared off similar to the original monocoque manxes. Can you post some pics of your car and get with Nelson Sparks. He is working on a list of the early cars.

Re the bumpouts in the sumps, they were added later. I am not sure if the bump was added prior to the big opening in the back or is that came with the big opening change.

Chris