The flex pipes are to allow some movement between the headers and the exhaust. It supposed to help prevent hardware loosening, cracking, and flange gasket failure. Stock exhaust on older cars have enough movement to prevent problems. I added them more as a precaution than anything.
I added the glass packs to prevent droning at highway speeds, and partially because I was told I couldn't fit anything back there.
Nice looking cluster there, Slodoba.