areonca65t beat me to it. Definitely Speedex A7 - the wheels are the dead giveaway, to say nothing of the A7 hubs poking through them.
I'm not sure Speedex built chassis for sale though, and this car having A7 hubs lead me to suggest an A7 chassis, with A7 or maybe Ford 1172 engine. Back then there weren't many 1500s used by clubmen.
I was reminiscing about the old days before he co-founded Marcos with Jem Marsh at Silverstone at the 750 MC 60th birthday a few years ago. There was an immaculate Speedex 750 car there - his actual Goodacre Trophy winning car.