Stupid question, I think I know the answer...

Do you have to get a handgun permit (or whatever they call those BS things) to purchase a pistol AR lower?  My guess is yes.  Damn I hate those permits, but they do cut down on my impulse purchases...

yup,  when i was at cmmg there was fella wanting to buy one and they told him he had to do the standard pistol paperwork/wait.

A lower reciever is niether a pitol or a rifle until the dealer logs in as such in his books.
I just bought two lowers from CMMG, one as a rifle the other as a pistol. For the rifle it was the same as a rifle purchase, give them the money, fill out the form, a call to NICS.
FOr the pistol I had to get my permission slip from St. Charles county sheriff.
So yes, to build a pistol from a stripped lower you must purchase it like you would a pistol.