I think that would all depend on how you mount the heat exchanger, and also on which exchanger you go with. Some are smaller, and could be mounted somewhere else. Hypa (from that link) had a slightly different mounting idea. He did have to modify the bumper beam a little, but I'd say 90% was still there. All depends on how comfortable you are with cutting a little material away. You could also go with the JDM bumper beam, which would also save you on some weight.