Position the vents in line with the edge of the front grill towards the rear of the bonnet. Then use a deflector plate on the front grill to direct air over the top of the engine this will cause the hot air to be pulled away from the engine bay and out of your vents.
Mk1 FRS owners have been doing this for some time and seen a good reduction in temps.

I would also advise a low temp stat and alloy radiator.