Yes, 530. 90 links sounds familiar, but I would have to check the manual to be sure (can do, later).
The cheapest "industrial grade" bulk chain (ie it comes on a big roll and they cut off what you need) will stretch rapidly compared to a modern $100.00 chain. If you are replacing chain it's best to replace the sprockets as well... worn sprockets will stretch out a new chain way fast.
Best value is probably new sprockets (about $50 - $80 for the pair?) and a decent boxed motorcycle chain - probably in the $50.00 range.
You don't need a super strong chain (you have under 40hp after all) and don't need a riveted master link: the clip link is plenty strong enough for a 400F.