specs are for a 2.6L engine 4ZE1, 1991 Isuzu Pickup
7 3 1 5 9
8 4 2 6 10
First Stage 57.8 ft lbs
Second Stage 72.3 ft lbs
Ideally you would use new heads bolts if you can find them.
Re-torquing shouldn't be necessary but all engines are different so you might need to consult a factory workshop manual or perhaps re-check the headbolts in 1000 miles or so.