The proper shroud and the the core support baffles are a HUGE deal on an AC car. You have to have them or you'll have problems. The mechanical fan will move way more air than the electric fans if the shroud is correct and the fan correct.
You could probably save all kinds of weight and complexity under the hood if you used the right OEM fan, shroud, lower radiator seal, frame horn seals and thermostat.
The way your mechanical fan is setup now it's just using up HP circulating air hot air around under the hood. I doubt it's pulling any air at all through the radiator at all.
To be honest, with that setup you have now, the first thing I might try is removing the mechanical fan altogether. If the electric fans are doing their job you shouldn't need the mechanical fan, you've got a decent amount of potential cooling power there. I'd bet the prop wash from the mechanical fan is destroying the efficiency of the electric fans.
That has to be one of the worst mechanical fan-to-radiator arrangements I've ever seen
But ... beautiful car.