Never had a Volvo apart, but I can't see the copper lines providing enough heat dissapation to be a concern. How the lines are terminated might explain why they used copper, compression or flare? Braided stainless would look nice, but honestly probably not worth the cost unless you are making the overall engine pretty as well. I'd probably opt for function now and get that craft on the water. Maybe repair the copper if damaged? Now one thing to consider is that copper will shine up nicely, and stay that way with a clear coating. Worked on many show car fuel systems that looked classy in bright copper. Just some thoughts.