Using Munchkin Code on Multiple Domains

My company has several websites but we only nurture leads through one domain. I would like Marketo to track activity from all of our websites but we would never send emails or nuture from our subsidiary domains, just the main one.

For example, we currently have 6 websites:

DomainA.com - lead entry point, main website that talks about all products and our whole platform

ProductA.com - Subsidiary company

ProductB.com - Subsidiary company

InvestorRelationsA.com

InvestorRelationsB.com

InvestorRelationsC.com

Should we install the same munchkin code on all 6 websites?