it isnt... but it would surely be a cheap starting point if one wanted to weld up a header using a cheap SBF header and some cheap LSx flanges...
take a pair of these perhaps
http://cgi.ebay.com/ebaymotors/Ford-...86416006QQrdZ1
and a couple of these
http://cgi.ebay.com/ebaymotors/GM-LS...spagenameZWD1V
add a welder, and apply heat...
this should work with other headers.. and the port spacing might require some tweaking. but it will save a LOT of work
just my 2 cents
(and why isnt this thread in the engine section?)