are vortec 305's prone to blowing head gaskets/cracking heads?

i have a 96 vortec 305 that just gave up last week(water out the exhaust and a knocking sound). i was told by a race motor builder that these motors are not worth rebuilding, because the "heads are junk" and are prone to blowing head gaskets, and/or cracking the heads themselves. i just need to get it running as soon as possible, and for as little as possible, so that i can put my bike up for the winter.any help is appreciated. thanks .. ron