Nice find. Didn't know that existed, must have been taken while I was walking round the show as the bonnet is shut.
This video was taken at Cars in the park in Leamington spa last year. The BMW 1602 next to mine belongs to a good friend and an ex manta club member.
As Chris B mentioned, the car is heavily modified, running :
2.5l Vectra V6, R28 Omega box, custom mounted 4HA Scimitar axel with LSD, connected to the box via a custom prop.
There is a full build thread on here in the project section under, Work starts on the mk 2 , V6 A series