It has been a while since I've done the change. I would think some of the older box section rims would be close, but perhaps not close enough. I think we generally replaced spokes.
Are your spokes galvanized or stainless? If they are 30 yr old galvanized spokes, I'd probably go ahead and upgrade.
I was at our local co-op yesterday, and someone was using a very nice spoke cutter/threader machine. A bit of work, but possible.