With clusters that large it's very likely your clustering rules should be adjusted. Clusters that size imply that you have very large numbers of duplicates in your source data. If that's the case then no worries but that's normally not the case. Use can use additional fields to tighten the matching or if using match codes, increase the sensitivity of the match codes being generated.
I can't provide you more details on how to select the best record aside from suggesting that you read the documentation. The Surviving Record Identfication node by itself typically is all you need to build that single best record for each match cluster.
Ron
