1971 C20 custom camper longhorn had original dual exhaust?

[dads longhorn]

Hi experts. I was wondering if the truck mentioned had dual exhaust as original equipment, or did it originally have a "y" pipe joining the mid pipes into one tail pipe. Now, the truck has dual pipes all the way from the exhaust manifold to the tail pipes, (2 mufflers). The exhaust guy on the phone was suprised by that, and said the truck originally had only one tail pipe w/ a "Y" junction.

2nd question. I have a leak rusted through the exhaust pipe and need to get it fixed. Does the pipe have to be replaced, or can they patch the hole in the pipe? I don't recall if the hole is before or after the mufflers.

Lastly, the last exhaust guy (who replaced the cracked exhaust manifold and replaced mufflers) said because the truck was meant to carry/ pull heavy loads, that the diameter of the exhaust pipe should be bigger than what he saw on their now. So, what diameter was the original exhaust pipes? Should I get a biggher diameter (But I have no plans to put a camper on the back...yet).

Thanks for your help, in New mexico