I have replaced a few isuzu head gaskets in my time, and I have never had to replace my head bolts. I have inspected them prior to re-installment. Your biggest concerns isn't the head gasket, it's cracking the head. The cracks are pretty easy to find for most engine rebuild shops. When I've blown a head gasket, I simply take the head off myself, and then take it in to have it inspected. Sometimes it can be repaired, and other times it's just easier to get a rebuilt/pre-loaded head.

Keith
"AIR AMIGO!" aka 1994 Isuzu Amigo SAS with Toyota axles, 5.29's, dual ARB's, IROK's, WARN HS9500 winch, and etc.
Pacific NW Isuzu Off-Roaders
Timber Tamers #172