I drove and sold a G with a broken bolt under the core support. No the engine wont fall out, lol! You can literally have the engine mounted with just the trans and right mount by the coolant reservoir with no front or rear and no cross memeber and it wont fall out. You probably won't tell any difference but yes you are gonna have to drill the stud out and remove it and then replace the bolt. If some of the bolt sticks out you may be able to use a stud extractor otherwise you're in from alot of drilling and fun times ahead.
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