Jim, I did more research and the V6 motors go SLOWER with true duals or something similar. Your "Y" is what was recommended so I went with a TRU X-pipe magnaflow, "Y" pipe into a 3" single pipe leading to a 3" in/out Borla muffler out back.
Stacking a 65 SC pulley with a 178-185 crank pulley takes the SC out of it's efficient range so why do that or even try? Check out these SC's we have and you will find that 15,000rpm is the upper limit for it's efficient range. My 178/70 stack spins it at 15,750rpm ballpark. A 181/65 spins the SC at 17,265, a good 16% over where the SC was designed to make the best power. It may make good power at that level for a while but eventually will ruin the SC. A 185/65 spins at 17,646rpm's. Awesome torque down low but dangerous at redline or near, 5500rpm places the revs of the SC at 15,650.
I love the low end torque and as Jim states passing is within the regular driving characteristics of most of us and that is where I enjoy my car the most, on the interstate!
I also agree with you JR, drive the car where you enjoy it the most. Few of us go to the track every Sunday. Build it for the street and drive carefully on the street!