[DeltaP]

You really wont know what method to try until you remove the T/body. Wont hurt to try your locktite as well as the PB and hammer method,(my preference), or putting some heat to it if its cast iron as long as theres something to grab onto. I don't recall you saying what engine this is,if its cast iron or aluminum and if the bolt hole goes all the way though the manifold. If its broken flush,(Murphy's), you'll be drillin' it out. Just be sure to pack it full of rags to keep crap outta the manifold and to have something to "pilot" the drill bit to keep it straight. Removing the manifold would be best.