Second this on the brake clearance checking. I had an old west German steel road bike with 27 x 1 1/4" wheels and thought I could just swap in modern 700c road bike wheels and be happy. However the brake calipers on the bike wouldn't work as the rims were now in a slightly different location and wouldn't adjust far enough to reach.
That said you can get extenders and longer reach brake calipers if you're fully committed to putting a modern wheelset on, but worth checking everything will work/fit before going too far down that route.
Second this on the brake clearance checking. I had an old west German steel road bike with 27 x 1 1/4" wheels and thought I could just swap in modern 700c road bike wheels and be happy. However the brake calipers on the bike wouldn't work as the rims were now in a slightly different location and wouldn't adjust far enough to reach. That said you can get extenders and longer reach brake calipers if you're fully committed to putting a modern wheelset on, but worth checking everything will work/fit before going too far down that route.