gclid is just an opaque query param — what are you trying to do with it inside Mkto?
So as we understand it - passing that GLCID (the Google Click ID) is key to measuring offline conversions and associating that back to particular ad clicks in Adwords. Natively, Google Analytics knows online conversions, but since we do considerable volume offline (and that volume is no doubt biased towards certain products / ads) we want to supplement the online conversion data with the offline, giving a true picture of return on ad spend on an ad-by-ad basis within Adwords.
So if we can pass through glcid through a Marketo form to Salesforce, then we can link it with offline conversions / phone calls, and export back into Adwords.
Here's an example of a URL with the glcid, after an Adwords ad click - note the last parameter, that's what I'm after. That ties a user 1:1 with an ad click.
Any ideas? Thanks!