Yeah, the search function doesn't work.

I intend on completing a couple 0% recievers as show and tell items at a gunshow.  

I may or may not want to sell them sometime in the future, and I may want to have a gunsmith work on the completed receiver/firearm.

A.  Would I be required to forward information to ATF or pay an excise fee for an occasional firearm I've made for personal use and later chosen to sell?

B.  What is the mimimum marking requirements be - address, serial number, caliber.  Would:

Joe Smith
Topeka Kansas

0001

404 Jeffrey

be legally adequate?  

C.  With a serial number I chose as long as it does not duplicate any number I have given a firearm before?  Would I be required to provide ATF with this or these numbers?
 
Yes, I've tried searching through ATF letters I've found online, but I could not find a definite (i.e., ATF opinion or legal) answer.    

If you made the gun legally, then there are not any required markings.  Manufacturers are required to get them, though.

If you want to put on makrings, you can pretty much put anythign you want.