"Then why did GM keep upgrading them? What's the magic hp # that breaks these rods if no one here makes enough?"
Your wit astounds me. GM didnt keep "upgrading them". They switched to a powdered metal cracked rod. It may have been cheaper to produce and use then the old style. There was no reason to "upgrade" them.

There is no magic HP number. The fastest front wheel drive 3800 in the world ran stock L36 rods and probably still does. Only did they recently "build" the block so that I assume they could advertise the motor as being a ZZP motor. Of course, Im sure they wanted to siphon out as much power as possible which could be another reason.

I had a 67 Mercury cougar and when we tore it down to be rebuilt it had 5 different size pistons in it and My Brother's Grandfather in law worked for Chrysler for 30 years and he said that, that was quite common for chryslers and he said it's alway's good to have them balanced...

------------------
Ghostwalker

..The buick 30,,3.3,,3.8 V 6 was one of the best engines GM ever produced it is a sweet heart the buffons at GMengineeringmade some collosal boondoggles <BUT they got this one right Forget the super charger,, unless you want to rebuild the engine
..the regular 3.8 gets 2 to 4 Mpg BETTER than the forced air ,,it will get better MPG than the 3.4.
The 3.8 is a smooth running V6 that will give you what feels like V8 performance ,, this engine pulls good and you can run gearing for better MPG and still have macho pull..
you can port the head mildly ,port match and come close to the supercharger performance,and improve MPG with Americans demanding $5.00 a gallon gas some day we will have it
The only reason to use a supercharger is drag racing around town ..for a daily driver you can not beat the Buick V6 SUPERB,EXCELLENT ,OUTSTANDING..I CONCIDER THIS ENGINE THE BEST SWAP FOR A FIERO ,BECAUSE IT HAS EXCELLENT POWER ,YET DELIVERS EXCELLENT MPG & ONLY A TAD HEAVY
i WOULD TRY TO FIND A RUNNING CAR CHEAP GOOD ENGINE UGLY EXTERIOR ,,HOPEFULLY SOME OLD SENILE BEAVER TRAPPER LIKE MY SELF OWNED IT ,,JUST PULL THE ENGINE OUT ,CLEAN IT OFF DROP IT IN THE FIERO..I would be all a tingle if decent headers could be fitted ,yes she was an expensive looking woman, but when I found out she was driving an NA buick 3.8 Fiero,I swooned & worshiped her for the remainder of my days ..

Get the cheapest "good" 3800 S2/S3 motor you can find, get new gaskets and swap them in and be done with it.