Forget about the rear. I did see once car that had one mounted on the cross rail over bell housing. That seemed to me like it would act more like a preheater. As I look at the photo of his installation it look to be on the far left (facing the vehicle) behind the bumper and ahead of the headlight bucket. You could do that. Another choice is to use a laminar type oil-to-water cooler. http://www.laminova.com/products/oil-coolers I put one of these on my historic race car because of front end packaging issues that limited the size and placement on an air cooled unit. That could be located in the engine compartment but on an already overly taxed cooling system like the Bora's I'm not sure there's much point? That does eliminate the long oil lines require to get to the front which are a PITA for full oil changes. Maybe he has an electric oil pump to help with that? Once emptied it's better to fill it by not diverting all the oil from the engines oil pump to do so. A thermostat will help you prevent that. It will trickle fill the cooling system when the oil is cold. But the thermostat would need to be close to the engine's oil oil pump and not at the front of the car. An oil priming system could also help. I have one of those on my 84 Biturbo which does also have air oil cooler up front. That car also has factory liquid intercoolers, one for each side of the V6. Talk about hoses and PUMPS!