Page 3
  Step 8: Time to drill the spreaybar hole. I've built this fixture to make it easier to set the intake hole on the same plane as the Y axis. Use a spot drill followed by a #60 drill, used to start the hole so it doesn't break out into the intake hole and finish with a #36 drill. Location is .100" from the face of the intake and .0245" from the intake hole. I spot the surface with a 3/16" endmill, flip and spot the other side.
  Step 9: Back to the lathe to cut the shank off. Leave 1 1/2" from the backplate sealing surface and make sure you have enough clearance so you don't hit the case on the compound or cuttoff tool.
  Step 10: Time to contour the front end. Build a mandrel with a dia. of .499" to seat on the bearing surface, .600" to clear the backplate bore, drill and tap a  hole to accept a 5/16" shoulder bolt that goes through the crank bore to hold the case. Use a V-block and vise it up making sure the head is on the same plane as the X axis. This is a tricky operation, trying to blend all the contours.
  Step11: Back to the lathe to cut the front bearing bore. Build a mandrel to accept the case, 5/16" step and .4998 step for the bearing. Make these a tight fit, tight enough to slide the case on but loose enough to take off. I sometimes use tape to make sure it stays put while I machine.
Build the mandrel and make sure you make contact in two places, the crank bore and the rear bearing. Use an indicator to check if the case moves, if it moves at all you don't have the proper fit to align the bearings.
  The picture above shows yet another version, it gives me more room to allow the use of a spring starter for Mouse II, by making the intake smaller and recessing the thrust washer into the case to avoid contact with the spring.I use indicators, picture to the right, on the X and Z axis when doing the front bearing bores. A .001" resolution for Z, depth, and .0001" resolution for the compound or X axis. Measure the bearing your using and cut to minus .0003 for the bore by .124" deep.
Step 12: Admire your work.