Any 3/8 bolt nuts and washers will work as long as the bolt is long enough, 2" should fine.
The DP to stock mid pipe on my wagon has 10mm X 1.25 bolts about 2" long with washers and a lock washer under the nut.
Get them from any store that sells that stuff.
Use anti-seize compound on all threads.
I also have a Grimmspeed 2X thick gasket there. Both cars have that gasket.
210,000miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.
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