Get a comp test
Run some engine oil flush and change the oil
The noise could be fixed wirh a engine oil flush, new valve spring or lifter
If the comp tesr is good pull the rocker cover and have a look
It might cost $80 to fix, flush and new oil, or a valve spring, or it might be a lifter which is a head off job.
More investigation into what is "actually" cactus
Finding a good wrecker LS nowdays is getting tricky, finding a good cheap runner is impossible
It is getting to the point that getting a basic rebuild is the cheap and easy option