Is it a sin to swap out '80s campy components
 

Just musing...

Would it be sinful to switch out a 1980's C-record groupset on an italian frame of that era, cold stretch the rear triangle to 130, and put a modern Record group on?

Seems like the usability gains would outweigh the vintage-ness. The alloy cranks look nice, though...

Yes

I think it is fine

How long has it been since your last confession, my son?

There's some considerable sin potential in putting recent Campy on an older Italian frame, depending on how recent you mean. My ownself, I'd say it's got to be silver, and the chainrings have to have 5 mounting holes.

You could get out from under the vintage gruppo without too much trouble, though.

Neo Retro is a thing
Go for it!

I'm not a huge fan of NR/SR other than it's nice to look at. I still have 1 NR bike and some parts hanging around for some future project that won't get ridden much. Biggest issue for me is limited gearing options. There are local hills that I might not be able to get over anymore in a 42-26 low gear. May not be a concern for you though. For myself I might just swap the crank for something vintage with smaller rings, and some better shifters.

You could also go for a middle of the road approach - like early 90s 8 speed stuff. It looks at home on most any older steel frame, works fine and is not very expensive.

Much depends on what frame it is fitted to. If it is a mass-produced frame without any particular provenance, go ahead. If the frame is a one-off from a particularly-respected frame builder, you would be better to simply sell the whole bike and use the money towards a more modern bike that was already foreseen for the components that you want.

Is there any real difference between a lugged frame made in Italy in 1986 and a new lugged frame?

Depends on the frame, shame to split up an original build.

My '80s Campy group was originally built on a Cannondale. It is now on an Italian frame. I'm glad I didn't romanticize the build too much - I like the bike better now.

Nowadays, only a few marques still make italian handmade frames for a very limited weird clientele, so i argue they will be of a better quality, because they are hand-built in low numbers and often by just one guy who knows what he's doing.
In the 80ies, they were mass-produced in the worst possible way, in manufactories, which lead to widely spread quality. Some came out good, some were pretty bad. And i don't mean the paintjob, which typically has more bling than attachment to the steel tube, and so was bad no matter what.
On the other hands, 80ies lugged frames that are still riding today likely have passed the quality test :)

It's just metal and plastic.
Also some of that old stuff really sucks.

Somewhere along the way, E-Ritchie opined that the lighter lines of classic frames looked best with the lighter lines of a classic group set and I tend to agree. So for me, 8-10 Campagnolo, preferably alloy looks best, as do quill stems.

From a rideablity standpoint--anything from that range is so much better than NR/SR and I wouldn't hesitate.

I had C Record on my ‘86 De Rosa, performance was OK but when I had a mechanical issue with the RD, I used that as an excuse to put an 8 speed Record Ergo group on it. A compromise of sorts, I didn’t cold set it, and it works fine. If the switch makes you ride the bike more, then do it!

Use the nice silver crank then...And maybe even the front der..lever mounted shifting is nice..