Looks legit to me, and I've spent a great deal of time exposing hooky Land Rovers
On the DVLA it is listed as a 1953 build, but registed in 1976. They state that it was rebuilt in 1976, so obviously went through some kind of DVLA check at the time, otherwise it would have kept the1953 date/reg..
I don't think the new or more recent rules on 'Modified/Altered Vehicles' can be applied retrospectively.
Plate is a probably a personalised plate, so not relevant and lots of older Mogs have uprated dashboards and stuff.
I'm a sucker for a fat tyred Mog, and the Pinto with 5 speed box would make for a lively and fun motor. They've obviously spent some quid on it, with the trim, hood and interior, and those split rims don't come cheap.