Some pulleys have two holes for a "Special Tool" that you insert into the holes to hold it still while tightening the bolt. If you have a welder you can make it with a couple of bolts, a grinder and a piece of angle iron. Others here have made one with a couple of pieces of flat stock bolted together. Or you can use a chain wrench and piece of belt to cushion the chain.

99 Gen 2.5, fixing blown head gasket
89 SWB- 33's, ARB Front locker, SR rear locker/axle, SR F brakes, winch, WST Offroad Armor all Around, 2.85 Aussie T-case Gears (SOLD)
Sold: (2) 95 SR's, 86 SWB, 90LWB, 91 LWB
-Can Change a timing belt in my sleep..