I would change:

Headgaskets
Head studs (they are NOT re-useable, they are TTY bolts)
knock sensor wire
valve cover gaskets
PCV valve
any other leaking seals / gaskets.

While you're in there, i would take out the fuel injectors and get them cleaned / flowed.
timing belt, idler bearings, water pump, thermostat
coolant

<img src="/forums/images/graemlins/notooth.gif" alt="" />

89 4Runner
3" BL, M/T locks, 33"bfg mt, bilstein, Kayline, tubebumper, toyotafiberglass panels
TBI: Elocker,3.4 w/ORS,b+b,S2Sstg2cams,arias pistons,P+P intake,TRDs/c,URDpullies+7th,downey headers,MAPECU2,WEGO WB, SupraMAF,walboro255,stg4clutch, EPaOo2 sim