Try and find a bigger one!
But, it should do fine as long as you don't overdo it. I mean its much better than those two little holes in the radiator the oil goes thru.
And make sure it gets as much airflow as possible.
Try in front of the radiator using those special cable ties (one side is long with a square end bit, and the other is used to clip in) that have cushions to prevent the constant squashing of the fins on the radiator and cooler. Try rare spares etc.
the one i have at the moment is positioned in front of the radiator (nothing else infront of it except the bumperbar (which has slots in it where it is positioned) - held about 1 or 2 cms away from the radiator with proper metal brackets set up to hold it there (is also on a slight angle leaning forward - so the top is about 4 or 5 cms away from the radiator, bottom is about 1 or 2 cms away..) - aparently this is how the car came stock (from a n/a calais that had a "towing pack" on it - which means it got the tranny cooler from factory).
i'll measure it up properly and take a photo of it if you want - i suppose that will do till i can find a larger one to put on.
not to scare you but i had a 2 speed powerglide in my vl with a 5,200rpm stall converter...i would drive that car nearly everyday and thrash it on the weekends even take it for a cruise down the coast...mind you i use to rev that engine to 8,000 rpm when racing even pushed it to 9,200rpm...(not a good idea but when the tyres let go when your racing at 160klm plus theres not much you can do in that split second..cause the engine goes boooom)