where can i buy booster boxes of the out-of-print marvel overpower
cards including IQ, Classic, and X-men overpower?

I have a plastic bin with who knows how many overpower cards at least
a couple thousand in it they are opened and some were used to game
with back when the game was in print others are virtually untouched
but opened

this   first one is a list of damaged boxes for reduced price
http://www.potomacdist.com/damaged.asp
this is new boxes 
http://www.potomacdist.com/list.asp?A=o&r=314

I hope that helps you

I have been to Potomac before, but they, like any other store I have
been able to find online, do not have many choices of cards,
particularly not the sets in which I am most interested.  If you have
Overpower collections for sale, I would be interested in them.  Please
post comments here arranging contact.

I have 1995 Overpower starter decks,1997 Monumental overpower booster
packs, 1995 overpower booster packs, 1998 Image overpower expansion
set packs. All are unopened. I also have single cards. LMK what you
are looking for. I will make you a great deal and I will pay the
postage.
Thanks and have a great day!

I'm interested in it all.  Let me know how you want to contact each
other.  I can post an email address if you wish.