Congrats on getting the Plus 4! (I had a great time with VICMOG when last in Melbourne.) Give my best to Elwyn and Neville Crawford if you see them.
Can't help on the engine number. But, re: the glove box, I don't believe that the factory produced 60s vintage +4 dashboards, with doors on the glove box, unless of course they were accommodating an special request of the first buyer.
There are however many, many cars with dashboards that have been produced outside the factory. And, many of these do in fact have glove box lids. And, many of these do appear to be of 'factory' quality or better, created using original specifications. That may be what you have.
