The Volvo thing is a good idea. Go to the junkyard and get this from an 80s turbo Volvo. They came with a pretty large air-oil cooler with a sandwitch plate adapter on the oil filter and 2 oil lines. The sandwich plate is about half the thickness of the VW cooler. It fits our cars. It should work well for your application which is low speed, high temp operation where longer warm-up cycles are not a problem (the stock VW oil cooler helps warm up the oil). You might also need a VW oil filter adapter or at least the threaded pipe from a car that did not have an oil cooler as the threaded pipe is much longer on the models with the oil cooler.