I can answer part of your question as I looked at an '83 610 just the other day. The canti springs on the '83 are externally coiled. If I was looking at it right and remember correctly, the fork side of the coil didn't actually go into a hole in a tab at the base of the fork mount, but maybe just interated somehow with the fork mount or the fork itself. The later version canti brakes, of course, had/have an internal circular coil with two 90 degree bends, one inserting into a hole in the brake housing and the other inserting into a hole in a tab integral to the canti post on the fork. Below is a pick from velobase



Afraid I can't answer your questions re a modern recommendation.