Not sure if you were using water/meth or not and if so if you stopped as it helps keep the valves and piston tops clean.

If leakdown is fine then rings and ring lands are good so I would not worry about the bottom end and spent the money on cleaning up heads as with 100,000 miles I would at the least put new valve springs in, check all parts for valves that are in the top of head and check that pushrods are true.

We have teammates that have 140,000 miles on 97/98 C5s and have boost on them.

Issue is that the early LS1s had oil fume/pressure buildup issues by crank so at the least if you went with a 2001 and newer LS1 or LS6 block if doing a engine swap is stronger.

We tend here to re-pin the 80 pin PCM connectors and use the 99-03 PCM and flash as a 2003 and whichever trannie is used when reworking 97/98 cars. The PCM is faster and has more and better tuning tables.