Yeah I'm going -10AN lines no matter what. Was just wondering if the housing itself necks down too much. I didn't think it did and will assume it doesn't unless it shows otherwise!
As for 180/190 vs 250- that's up to the user to decide! The beauty of choice...
Also, the factory T stat probably doesnt flow at as high a rate as the Mocal when fully open, so it's not just the trigger temp that matters. The oil will take the path of lesser resistance so in factory tstat setups the flow through the cooler is probably less at operating temp, but I dont know by how much.