should i avoid a black/gold bolt and carrier?
Almost all will have a re-finished bolt with electro-penciled serial numbers. I found one SVT which I added to my collection that had an original silver bolt. These are far and few between.
The color of bolt is personal preference. They come in silver, gold, copper, plum and black. The black ones are less common - one member sold some for a premium back in the summer.
Another option is take down the bolt, place in a vinegar bath, use some copper wool if needed after a 10 minute soak, rinse in hot water and oil = silver bolt with original finish.
This is why I don't put a premium on silver bolts; any regular joe can convert their bolt back to silver if they wish. The end result is how do you know if the silver bolt is original or vinegar bathed?
I have some thoughts on the subject of Milsups. With a refurb rifle the authenticity has been ruined, but it now has new authenticity as even refurbs follow historical patterns. So the owner has two viable options:
1. Restore the rifle back to what is should look like (remove shelac, silver bolt, correct parts for the year, etc.); or
2. Leave it as is - as even a refurb is a legit variation of the rifle.
In the end it is your going to be your rifle, so do what you want with it...heck go sporterize it if you want...it makes the remaining rifles that little bit more valuable.
I was guilty of restoring RC K98's about five years ago when I first got into collecting. Swapping out parts/stocks/removing cold blue etc. The result was a much better looking K98 but some of the RC historical value was lost. Now I keep any new RC's I pick up as is. They are what they are and there is little use polishing a turd (but I would rather hold a rifle in my hands any day).