318 camshaft timing question

I have a stock 1988 roller cam 318 that I rebuilt some 30,000 miles ago. Stock cam, lifters etc. Dingle ball hone rebuild and freshened up #302 heads. Cast 4bbl intake, Holley 390cfm and a MSD ignition. Runs great, get 14mpg in my Ramcharger with 3.21 gears.
The question is that this dude is loud. I just switched from the dual exhaust to the factory single 2-1/2" exhaust and catalytic converter. I thought that the duals were the reason why it is loud, but not the case. It's loud at the engine especially for a stock Ramcharger.
Another issue I have is It needs 93 octane or the thing will ping like crazy. I have the ignition timing at 10*, total 32 and with vacuum like 50ish. I'm using the med-heavy springs in the MSD distributor and the factory advance stop in the MSD. It doesn't matter what I do timing/distributor wise, it still does this.
Now, i used a stock single link timing set, but I do not remember the brand (I rebuilt it 5 years ago) but it has me wondering if it is off and it has the cam really advanced and causing me to have high cylinder pressure, in turn causing the pinging and such. Every year the dude also fails emission testing with high hydrocarbon and Co2 with my EGR hooked up.
Any thoughts on something I may be missing?
Thanks!
Paul