Cooling issues, could use some advice

We'll have to agree to disagree on that point. While true that it will affect airflow in it's immediate area, I've yet to seen an engine oil cooler big enough to disrupt airflow for the whole radiator and even the oil cooler heated air isn't all that large of a delta-T to have a huge impact on the radiator's cooling ability.
Still, best would obviously be if it weren't in front of the radiator.
The original oil cooler from the RX-7 would be a good choice if it is still around. Very wide and not very tall.