Adams' Apple said:

Case75 said: Bottoming out is when the distributor drive gear is too far down to mesh properly with the cam ....

Whu? S'plain this one?

Dave.....did ya remove the plug wires from the cap? Ya may have gotten them off a notch. It's also possible the original dist was off a notch, and the wires were moved around to make it right....when you installed the "rebuilt" dist, and put the wires back, they would be off.
If yer sure the dist housing went back in exactly where it was, it's still possible to be off a tooth. The dist shaft turns as it comes out....as it turns, it also turns the oil pump shaft. Getting the dist back in usually requires goin PAST where it came out, in order to get the pump shaft lined back up.....my bet is you are one tooth off. The best way to fix that, or determine the problem is to get the dern thing up on #1, and see where the rotor is pointing. If it's pointin at #8, or #2, just move the plug wires a notch.....it's easier than taking the dist back up and trying to do it that way.  At least it is for lazy fellers like me....

Or..you could just twist the dist around, if ya have enough room, but ya prolly don't, if ya have the shielding brackets still.

Copied from Performance Distributor's website:

Problems with irregular distributor gear wear can be caused by the distributor being “bottomed” out on the oil pump or cam walk. This problem can be easily prevented if the proper precautions are used.

First, we will cover the problem with “bottoming” the distributor. Bottoming of the distributor usually occurs when engine work such as the block, heads and intake have been milled. This will allow the distributor to sit farther down in the engine. The best method for checking the distributor to find out if it is bottomed, drop the distributor in the engine with no gasket. Also, make sure the cap and rotor have been removed for this test. Firmly hold the distributor against the intake with one hand and with the other, pull on the top plate of the main shaft. Very Important! Make sure you grab the top plate where the weights and center cam are riding. Do Not grab the reluctor (the part the rotor attaches to) because this part has up and down movement at all times. By grabbing the top plate you are checking for any up and down play in the shaft. If the shaft has up and down movement, you are now ready to install the distributor permanently by adding the gasket and installing your hold-down clamp. If there is no up and down movement in the shaft, then the distributor is bottomed on the oil pump. You will need to add a nylon distributor shim of correct thickness until the up and down play is achieved. Nylon distributor shims are available from Performance Distributors in thicknesses of .030″, .060″ and .100″. When the correct shim has been determined, add the gasket and proceed with the final installation. Always use a gasket with the shims. Warning! Do not stack gaskets in an attempt to raise the distributor height on the intake. Gaskets will compress and the distributor will eventually bottom out. Always use a shim when necessary.

Another method of checking for bottoming, is applying machinists dye to the distributor gear. Spin the engine by hand several rotations. Remove the distributor and inspect the wear pattern. You should have an even pattern through the middle of the gear. If this is not the case, add distributor shims until the correct pattern is obtained.

If you have checked the distributor for bottoming and you are still experiencing irregular gear wear, then the problem could be “cam walk” or “cam run-out”. This condition is where the cam is moving back and forth as the engine is running. Use of a cam button will help prevent “cam walk” but is not very effective if you are using a stock timing chain cover. The stock timing chain cover is made of tin and flexes easily, which can allow the cam to move even with a cam button. Use an aftermarket steel or aluminum timing chain cover that is reinforced for extreme cam loads. This should solve any problems with “cam walk”.

Adams' Apple said:  Otay...I get that. BUT....that particular scenario will also shed tons of metal, both from the dist gear AND the engine block where the gear is now rubbing. It would normally also lock the distributor shaft down, depending on how tight it is bottomed.

I was thinking maybe you were suggesting that the dist gear was on upside down.....don't laff...I've seen folks do it!

Dave made reference to a drag on the starter so that's what came to mind.  Could be any number of things that I can't even think of and I hope it's something real simple. I'm not a mechanic but I try to help out where I can.