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It depends what you want to do with the car and how much power your looking to make. L98s dosent make power past 4500-4800rpm without some serious modification. Personally if there was no smog/emissions I would pick up a lsx and put a carb on it and be done, very easy to make 450-500rwhp for your price range with an lsx.
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I'd sell and buy newer....93-96. You'd p/u air bags, more hp, traction control, and a newer car that will help fend off father time.
Tuning a speed density car is a bit more of a challenge (like your 90). That process alone may cost more money than you'd think.
Since $3500 is your budget, it's hard to see where an LS is in your future at this point. If it were, it's definitely a better platform for modification.