Do not use a inpact, you WILL break the bolts
Spray PB blaster, let it soak in, spray again, let it soak in, do this 3 or 4 times.
Hit the head of the bolt with about a 3 lb hammer, do this 3 or 4 times, spray again between hits (hard hits).
Try to move the bolt with a wrench, NOT a breaker bar...