About to be a bit of a long post, trying to make it as concise as possible.
The 3800 was actually well built. It depends on the builder and how well it is tuned. Some guys run junkyard stock motors to the grave with 20psi of boost or put a big stock eliminator cam in, run it to 7000rpm and keep going. They can handle a lot just stock, but it will show that it is worse for wear after extended use/abuse.
Mine was run pretty hard and at 120,000miles it still had the stock hone visible in the cylinders and no ridges. It was just badly coked up with oil sludge.
It is by no means a hot rod engine from the factory, you can thank the bean counters and the good old no-competition stance with the V8 performance packages. The 3800 SII had prototype aluminum heads (only a few sets exist) and they did a test of an L67 (supercharged) V6 Firebird before the LS1 came out. That thing ran close with LT1 times in the 1/4 mile.
Supposedly they have relatively close tolerances and the mains/cam window don't have a lot of deviation stock from the factory. It is recommended to get them align honed during a performance build especially when using ARP hardware on the mains and rod ends.
Now, they are all steel crank setups. The crank is good for closer to 1000hp from what I understand. The oiling system needs some things optimized to make sure the rotating assembly doesn't get starved at that power level though.
The rods are the biggest thing. The L36 rods are okay up to a certain point. One bit of detonation and you've got a hole in your block because they're just drop forged. All the pistons are hypereutectic. Melt like butter during knock or too high a cylinder temp.
The L32 rods out of the SIII motors are the best, good for around 600whp or more. They're powdered metal rods, closest to forged you can get.
The block is essentially the same between the SII and SIII. Cross bolt mains (can upgrade with ARP cross bolts and main studs to decrease crank deflection).
Biggest issue is the intake and cylinder heads for these cars. Stock, they flow poorly. A hand port garage job won't net you real gains and could hurt it in some aspects if you take it off in the wrong areas without a flowbench to show you what you're doing.
Bigger valves help, and if you get a sheet metal intake built, that would be even better.
There's reasons why this engine was on Ward's best engines list on multiple occasions from 1995 through 1997 and in the best 10 of the 20th century. They're durable and low maintenance. Take a beating and just keep going.
2000 V6 Firebird
●60°Inc. Heads & Intake●Intense S1X Cam●FFF Longtubes●Strano HP7 Package●T56 swapped●