That's why the system MUST be vented, the water in the rad only leaves the the rad because it has expanded. If it can't get out of the rad it will expand and pressurize the cooling system to greater than 16 lbs.
The 16 lbs cap allows the air ( or coolant if it's 100% full) to escape out...
My dad made one out of an orange juice bottle, he had it on his / my dart since the late 70s when I got his car it was one of the first things I removed.
The radiator tank can have an inch of air above the coolant. It dies not need to be completely full. In all reality, you could fill the rad to the top, go through several heat cool cycles and the coolant will find its level in the radiator. Maybe in the hottest heat of the summer it will loose...
100% normal
after the center clips are installed can you PRESS the cups either direction? DO NOT APPLY TOO MUCH FORCE just enough to see if there is movement.
What I see is the slot for the new cups is wider than the slot for the old cups.
Are the new clips the same width as the old clips...
Make sure your axle spline count is the same.
Is your diff guy a shop or a buddy? If a shop they might be able to get a clutch type cheaper that you can.
Also ...
The eBay ones are of Unknown quality. They may be fine especially for crushing but unknown how they last under harsh conditions
Here is a simplification on indexing the gear carrier.
All of the blue (gear carriers) centers are the same distance from the upper edge of the gray rod (the output shaft of the transmission)
The green gear is smallest in OD
The Yellow gear is middle in OD
The red gear is largest in OD
Note...
Try this.
Put your timing light on cyl #1.
Then point your timing light on the pass side of the damper. If you see the mark at about the 10:00 position you need a bolt on 67 273 timing marker.
Or do as described and make a mark on the driver's side on the balancer when the engine is at TDC...
My money is you want a 67 Dart cable as it has a threaded end on both ends, one larger for the trans and one smaller for the speedo.
This is the one on my 67 Dart right now. 61" long (WHAT I don't know, is the 727 speedo gear the same distance from the rear of the block as the 904?
This cable...
Sort of. They are inside the adapter the gear attached to. The factory service manual, available free download from mymopar.com has a cut away and install instructions.