I've seen worse. PB Blaster/Kroil/WD-40 penetrant/Seafoam spray are all your friends when it comes to these bolts. Spray liberally over a period of days and allow the cyclic heating and cooling of the engine work it in. I also find that using a six point or impact socket on the nut and hitting the breaker bar with a 2.5lb hammer is more successful at breaking rusted nuts and bolts loose without stripping them. Sustained pressure tends to strip heads more than the hammer technique.
