301 or 307 for affiliate links?

Want to avoid getting penalized.

[majjk]

Our affiliate program tracks referrers by grabbing a variable in the link that was clicked, e.g. domain.com/index.php?ref=MRSMITH

At the moment all those links get a 301 and is redirected to the same page without the variable. I believe I read somewhere that it might be seen as cheating by redirecting link juice from a great many pages to one single (or a few) page(s). It does somehow sound credible... Should I switch to a 307 instead?

Does it make a difference? Comments?

[majjk]

I think I found the answer to this on
[googlewebmastercentral.blogspot.com...]
i.e. to use link rel="canonical"