Jim, Let me add more detail.  My Superior XP360 b1a2 (constant speed, dynafocal rear governor, 8.5 comp. ratio) has the long mount and there is lots of room for the governor and oil filter. I also have the plenum which eliminates cowling seals.  My exhaust is by Sonic Headers in Princeton Mn, and is a 4 into 1 with pipes from right side crossing behind the sump.  Todd at Sonic Headers did a beautiful job, stainless, ceramic coated with heat muff for about $1200 based on my pvc mockup. It all fits without any cowling bulges.  I replaced one Slick Mag with E-mag, which is the best electronic ign (in my opinion).  The oil cooler is in front of Cyl 2 under the plenum intake.   Also, Superior has better factory support than Lycoming, you can get Bill on the phone anytime for advice.  Bolt on a MT 3 blade prop and a 2.5 inch extension and weigh in at total of 1140 lbs.  The E-mag uses Iridium auto plugs, $3 each