I could be wrong here but I definitely remember some people saying years ago (like, 10-15 years ago) that there were some G40's that don't say G40 on the logbook. Makes no odds to some people but other (purists) like having an original G40.
Take a copy of the chassis/VIN number to a VW dealer and they should be able to lookup and print out the original order/ similar stating what the car was originally.
Unless you know it was a GT originally, may be worth stating that (assuming you know for sure either way).
Yeah mine doesnt say G40 on the logbook and at one point thought it was a GT conversion. I managed to get a copy of the 1st registration from DVLA and it was registered with a PY code engine in June 1991.
...LOL just went to check registration month and id not realised that the copy of 1st registration actually says Model - Polo Coupe G40, Body Type - Coupe.
I think at the time all i was interested in was engine code to confirm if it was a original G40. Might have just forgot but im sure in the G40 register thread i used the engine code to confirm G40 and not the fact it was a G40 to confirm G40 LOL