I know there's no "real" way to tell if they'll fit, until someone buys them and tries them, but what do you think?
This is a picture that I stole from the Ebay posting, and then from their measurements I extrapolated the rest of the measurements. By my measures, I think they will fit. The only thing I don't know, however, is if there will be steering shaft interference, as mine isn't installed right now.
Oh, and BTW, I'd be running these in the down and forward position. Don't ask questions
http://cgi.ebay.com/ebaymotors/LS1-LS6-Stainless-Shorty-Chevrolet-Engine-Swap-Header-_W0QQcmdZViewItemQQhashZitem255edade50QQitemZ160505192016QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_2480wt_1027