I would defenitly advise against putting a loud mouth on a bone stock 305. Boon (Mister-Juice) has a loud-mouth on his Iroc, but it is a far from stock 305 and it sounds amazing!
I'm pretty sure you could use a 93-95 LT1 Loud Mouth, since your LG4 is single cat'd I think theirs only a different pipe bend somewhere in the system. Also if Im not mistaken the Loud Mouth is just resonator mufflers, any exhaust shop could fabricate that into a system.
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