Not had a look yet, but i think you are right about the intake, same size/shape runners and equal plenum are not going to do much for flow, but then there's little room for anything better, as for vent, i think behind the rad would help, but the heat generated by such a large/long engine also needs a way out for the hot air, but a vent further back may not work as it encroaches on the pressure change area in front of the screen,
have you removed the bonnet lining? and does it make any difference? may achieve the opposite in strong sun though.
Also been trying to find info on oil temps, but not turned up anything in a search!