Yup 87 only engine. All later use engine balancer and Oil filter in the pan and have several issues even before balance bearing dies.
When the balancer dies, very hard to impossible to replace even if rest of engine is recoverable and crank gear isn't wrecked.
replace the gear and install crank balancer to replace OE pulley.
See my Cave,
Cam Gears,
Cam Gear PFF archivecan do this w/ cam in engine or take out but more work to a lot more work depending how done.
Threads you make on cam to use press/pull parts maybe wrong. read both links and maybe search. Partly because can't/won't use exact same tools as GM.
1mm/
.040in in oil gallery plug is very small and most drills can handle tiny bits. need
variable speed dremell and adjustable chuck. Maybe small collects might work but a "real" chuck is way better. A flex tool/cable between helps a lot. Slow speed and light pressure or will break the bit plus helps prevent bit pushing in crap when pierces the metal.
Can get cam out w/o taking engine out but will require more access to lifter gallery to pull lifters out. remove OP drive. etc.
Avoid remove intake man. If you do w/ require gasket, use Felpro not others. Make different to stop some problems.
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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave