What hubs do you have ? If they are C record it would be nice to use Campag rims. I have just bought a pair of Omega clinchers, 32H, NOS from a reliable supplier on E-bay and I see he has another pair.
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the delta brakes work best with slightly wider rims, so you want to avoid too narrow a rim. Ideally you want 19 mm internal width as a minimum. The MA40 or its predecessor the G40 were great. The various Campagnolo rims were also good, but as already mentioned much depends on the precise period of C-record that you have.