The standard wheel on a Raleigh 3 speed is a 650A / 26 by 1 3/8, the hub spacing is narrower than a modern hub, and the axle itself is narrower.

Replacing the rims with alloy may not be aesthetically pleasing but from a performance standpoint... it will be like night and day.

I have rebuilt the wheels on just about every three speed we have and it cures these bikes of their greatest failing... braking when wet.

If it's a truly classic bike I have been able to source out vintage steel rims for rebuilds as running alloy wheels on a bike like my '48 roadster would be wrong... and it stops rather well in the rain.