Robert;

Brocken mounting bolts are not uncommon on that style bracket, when bolts vibrate loose and allow bracket to wear away at the bolt sides, eventually fatiguing them enough to break. Bolts are also in shear which really is not really right (should really have pins like engine to bell-housing where pins locate are in shear, and bolts hold).

...bottom line is that the brocken bolt remains are likely loose in block and fairly simple to remove (dremel a slot and unscrew). After extraction, check how badly threads have been damaged...down deep, they're probably OK.

There's not need to change to another manufacturer's mounts...replace motor mounts (including trans mount which is also in shear) with higher durometer Volvo mounts from 6 cylinder (PN 1206612). These work very well (and for a lot longer!), and don't transfer appreciably more vibration to frame....just make sure you use lockwashers and/or light duty locktight on hardware into block to prevent reoccurance of loosening.

Cheers