I second what Martin said about the shrouding, also a shroud to effectively reduce the gap between the oil cooler and the heat exchanger behind it should help airflow. Also quality oil. Redline 5w30 is a very good oil as well as other
actual full synthetics, motul, royal purple, mobile one etc. Do not run a heavier oil, that will just reduce your oil flow (and hence the cooling ability of the oil cooler) unless your engine specifically requires it for other reasons. Venting the engine bay through your hood or fenders should also help though it may be beyond the scope of your project.
PS ... dunno about the fan idea, I'm 99.9999999 % sure that during hard driving it would just reduce flow by adding an obstruction in the flow path... unless of course your fan is capale of moving air at 120+ mph, in that case your prolly good!