The Shimano 600 group sold in 1987 was a combination of 6207 and 6208 parts. The indexed shifters, RD and brake levers had 6208 part numbers, but everything else was marked 6207.
Hubs should be 6207 and would be freewheel, not freehub. You can make a 6400 freehub work with 6 cogs and the correct spacers. There's a guy on eBay who will make you a set of spacers to fit; he's a machinist who sells tools and spacers. You can find him by looking up shims/spacers on eBay.
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