That one is known as the "Vanguard Special" I used to own the other DeJoux GT known as the "Holden Special"
From my understanding the "Vanguard Special" was built by Kevin Lamb, on a widened TR4 chassis.
The "Holden Special" had a space frame and was built by Dennis Marwood. I purchased the car in the mid 80's fitted with a Holden 253 V8 by a previous owner Diana Coster, daughter of Don Coster, owner of "Coster Motors" formely in Dominion Rd, Mt Roskill, Auckalnd.
During the 6 yrs that I owned the car I made many changes including fitting Holden ventilated front discs, replacing the original burnt blue Cresta Discs. Replaced the original Cresta diff with a Holden 3.08 lsd. Rebuilt the dashboard using Jaguar instruments and a wood rim steering wheel. Better Radiator from a commodore, and yes I am the person that fitted the contentious MGB/GT sunroof, mainly because I happened to have one and the car got so hot inside as there was no air inlet. The car weighed 1060 kg and had a top speed of 140mph.