I'm looking to modify a "standard" Murray beach criuser into more of a chopper style cruiser, with ape-hangers and a brooks saddle and I want to move the seat back about 6-10 inches without chopping or permanent mod. Is there a seatpost out there that would right-angle back to offset the seat?

Search for "Layback Seatpost"

They don't make em with a 6-10" extension but it does make the angle you are looking for and I suppose you could extend it.

there's several here http://www.choppersus.com/store/category/8/51/Seat-Posts/

or, go through your pile of handlebars, and cut one yourself.

like this? http://www.bicycledesigner.com/partsmain2.asp?Type=seat%20posts

Edit- never mind, thinking about the wrong place, maybe.

really? I've ordered parts from them for years, never had a problem. One of my favorite places to buy cheap parts.