I found a small muffler shop in Royal Oak that would do the one-ball mod It's called TLC and it's on the SW corner of 12 Mile and Main (Livernois). The owner and chief mechanic is Scott Callahan, and he is your typical nice guy. I had spoken with him about some exhaust work on my Merkur and he was honest and fair as he declined the work. I told him that I appreciated that and that I would be back someday for some custom work. I stopped by on Friday night and showed him the pictures of the one-ball mod that I found here on NAM. He said no problem, $90 and to come by anytime. I showed up at 8:00 on Saturday just as he opened and dropped the car off for the mod. My wife and kid met me for breakfast at the Burger King and as we were driving away after breakfast, Scott called me on the cell saying that the job was done. The car sounds great (deeper at idle with a little more snarl at high RPM) and the price was exactly $90, even after I asked him to also break the exhaust nuts under the shifter loose for me (Helix short shift ready to go in when it's a bit warmer). I'm pleased with the work and told him that I would tell the other Michigan MINI peeps about his place.
TLC - 248-541-8300