I converted an 80's Nishiki road bike (CrMo frame and 27" wheels) to 700c wheels and brifters. I used Tektro mid length brakes and 700x32 tires. I also used an old MTB crank set (42/32/22) and removed the 22 chainring to allow the original front derailleur to work and not have to buy a longer crank spindle and the gearing was very good. Whatever cranks you choose, for a gravel bike you will probably need lower gearing than the typical vintage cranks (often 52/42 or 52/39) unless you live somewhere very flat.
I also recommend using brifters as when riding gravel you are often confronted with rough terrain requiring two hands on the bars and the simultaneous need to change gears quickly but this is difficult with downtube shifters. Note also that for downtube 10spd, only Durace shifters are available and they are rare and expensive so it's probably cheaper to get an olld set of 105 shifters off ebay. Friction shifting is going to be even more of a hassle when the going gets rough.