I would agree that Tortoise SVN in Windows Explorer would be the best way to use SVN with VB6.
The biggest change you will find migrating to SVN is the idea of "Check out" and "Check in" aren't exactly the same as "Update" and "Commit". . . thus, any IDE integration with VB6 is limited because VB6 supports MSSCCI, a check-out/check-in mechanism. I once used TamTam SVN (http://www.daveswebsite.com/software/tamtamsvn/index.shtml) with Visual Studio 2003, but stopped since I found it limiting. Merging/branching/blaming, etc. are very powerful features Tortoise SVN provides that weren't in TamTam. Tigris also has http://svnvb6.tigris.org/, but I have not tried it.
Again, while you quite possibly get an IDE to work with VB6, I would not recommend it since the greatest strength of migrating to SVN is to break the Source Safe philosophy of check-in/check-out.
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