Thank you for your imputs. The engine was never going to be a top end performance unit, it was chosen because it fit in the car and would make the build one of a kind. The easy and cheap way would have been a box ls unit or something similar.

The thing is that the engine was working really well, huge amount of torgh for this lightweight car. But 2 years ago it blew up, probably because of uneven combustion between the cylinder banks. As it was rebuild he tested the compression and noticed the problem.