Since I do have some experience with this topic I'll chime in.
Most people have mentioned it already .......
Stock LT1/stock fuel system + boost + 93 oct = roughly 550-580 rwhp range (depending on the type of dyno numbers are just that NUMBERS not Holy Law LOL the delta gains are where its at).
This has been debated and pretty much verified.
If you have a good tuner and not motivated by greed (more boost more hp) The LT1 is Very boost friendly considering its a high comp NA engine not designed for boost but these are stout engines really.
If you want to stay with strictly 93 octane alone and nothing else ... then yeah that's kinda of where the fun ends with the stock LT1 until fuel upgrades are added (LT4 fuel system, JMS, or inline LP pump etc).
However ...... if you want to play around with higher octane fuels or additives and/or add some water/meth then the fun doesn't have to stop there! At your own risk which is always the case LOL.
Right now I am over the 600 rwhp (dynojet) threshold and still on 100% stock fuel system .... but I run higher octane fuels (actually only 93 + 32 oz Race Gas additive Not Even full Race fuel) and have an AEM water/meth kit. The fact that I am able to do this while only running 5.5 psi to me is impressive for such low boost very efficient and cool running setup.
Lower cly/intake temps and higher octane = more fun to be had while boosting a stock engine like the LT1.
I am going to pulley up to my previous boost level before the ARH headers (was 7.5 psi) and my tuner (very well respected GM and Mopar tuner) said he expects another 40rwhp gain on his dyno (he has a mustang dyno so lower numbers). All he really wants me to add for that level is a JMS pump booster and that should be enough for my car.
So currently I'm at ~540 rwhp on his mustang dyno (over 600 rwhp dynojet) at 5.5 psi so at 7.5 psi he is expecting around 570-580 rwhp (mustang dyno lower number) which would put me at around 650+ rwhp dynojet mark all on stock LT1/stock fuel system plus a JMS at that point.
He mentioned that stock 6th gen ZL1s usually only put down high 490s rwhp on his mustang dyno so he and myslef were really happy for such low boost and still safe.
However again on just plain 93 oct and nothing else this just isn't possible or safe at those hp levels with the stock LT1. I got bored of the 93 oct only power level quickly so playing with the higher octanes/ water meth was well worth it to me but I realize some just don't want to bother with the extras and that's fine. There are many more ways to make power than just upping the boost so that shouldn't be the only metric being looked at.
If I go past the 7.5 psi level then I will definitely be going full LT4 fuel setup+ ...... but hopefully at 7.5 psi I'll be mid 10s at low 130s mph so hopefully that will be enough for a bit ? who knows LOL. Over 10psi and its drop in pistons and cam FUN just a matter of time i'm sure !!!!
Happy to say my stock LT1 has been liking boost since 2017
-Jon