This is going to depend on the shape of the handlebars, whether a rim-brake wheel will fit and whether a caliper brake will reach the wheel rim.
Bars: The stand-offs for the brakes on mine are brazed on the handlebars, but the bars are the same diameter, so I could fit flat-bar style levers and I don't think they'd get in the way once I'd taken the old brake rods off.
Wheels: You'll need to swap to a modern wheel for rim braking, so either a 27" or a 700c. Whether they will fit will depend how much clearance there is, because rod brake wheels are older 26 x 1-3/8" size which is smaller.
Calipers: This is where it might get tricky. Assuming the fork and rear bridge is drilled, you can fit a caliper brake. Something like old Weinmann calipers with the long stud and nutted fitting will probably be best. The issue is whether they will reach the wheel rims. Check the wheels will fit first, then buy your caliper based on how much drop they need (distance from caliper pivot to middle of braking surface).