Picture of the top of the distributor drive gear that stays in the engine block. See that the bottom half is larger then the top. At TDC, the large half must be to the upper left in the block. Watch the video
John Twist explains install the dizzy...
This is the bottom of the distributor that fits into the drive gear. It fits only one way. This is called the "offset drive dog"
In other words, you must install the cam so that the rotor points to cylinder one such that the offset drive dog is oriented with the large offset to the upper left. Additionally you must install the drive gear correctly, the large section to the upper left.
Go directions & pictures: http://simonlacey.com/pages_new/content/distributor%20rebuild.htm
Tested the vacuum advance using a tool from advance auto. It failed, so sending unit out to Advance Distributors to be rebuilt. advanceddistributors.com
Solenoid PULLS to engage, so pull the plunger out of the solenoid to slip it over the arm.
More borrowed stuff..
There are two possible problem areas not mentioned in the distributor re-assembly instructions. The first is that the hole for the cross pin in the distributor drive dog and in the distributor shaft is normally drilled slightly off center. This means that they are in proper alignment in one position, but slightly off when assembled 180 out. I use a scribe to make a reference mark, or witness mark, on the drive dog and a Sharpie marker to make one on the distributor shaft. The shaft is hardened steel and often does not take a scribe mark.
The second possible problem is when the points cam is installed on the distributor shaft and engages the centrifugal advance weights. The points cam may be installed one of two ways—correctly and one hundred eighty degrees out. To install it correctly, remember that the distributor drive dog “ears” are offset to one side. If the ears are offset towards you, the notch in the points cam should be to your left to allow the rotor, which engages the notch, to point to the number one distributor cap terminal. Other than these two items, I have found no problem areas associated with replacing the distributor shaft bushing.