I mounted an Aimpoint 5000 on my pet 686 Power Port with no problems. However, I only used cartridges with jacketed bullets. My fear was not so much fouling the front lens as much as clogging the expansion chamber for the port as I'd seen a friend do to his 629 Power Port.
My choice for mounts is Weigand. Your 629 Power Port should be drilled and tapped for a scope mount from the factory, so installation will be fairly simple. If you can turn a screwdriver and an Allen wrench, you will be fine.