That's a nice addition, my first thought on seeing the motor and gearbox was early Lotus/Coventry Climax.
As it's a bored out version of the Hillman Imp engine it is pretty much a 40hp Coventry Climax motor.
It's going to look and sound great, will give enough go to be enjoyable and has some interesting tuning possibilities.
Good luck with fitting it, I hope it's not too much of a challenge.