The Raleigh pattern brakes changed parts over the years as well. The 58 Colt I restored brakes have different parts than the 72 Sprite 27" I'm working on now. Different nuts, bolts, threaded vs un-threaded spots on the bolt, bushings vs none. That concave nut with the recess for back side of the spring mates with the front half and the pairs do vary from different production eras. You are going to have to find the same vintage nut in order to be able to use the existing brakes. Try oldbiketrader.co.uk if you can find an old part manual from the correct time period and match the part numbers to his stock.

The assembly on your should look like this greasy work in progress


Part numbers: