I'm sure they gave you "turbo" mufflers. just awful.
Try swapping them out with a chambered design. I like the inexpensive 2 chambers. I think jegs has them under the Jones name and Summit has a house brand muffler. I have them on my 71 and they sound good, not too loud, and not expensive.
https://www.jegs.com/i/Jones-Exhaust...B2441/10002/-1
https://www.summitracing.com/parts/sum-638221