Hi - we've been working wih eConnect since version 7.5 of GP - so yes, there was a version for GP 8. This wouldn't be supported any longer by Microsoft - also the version 8 install of GP wouldn't be supported. I'm not sure you could even purchase eConnect for GP 8. It was a bit buggy when it was released first so if you have the choice, upgrade and use the latest version of eConnect.
When you say using VB8 for integrations...thats a very broad question. I'm guessing that you are talking about writing directly to the SQL tables? This is something I can't advise you enough to steer clear of. We've come across too many botched attempts over the years that created all sorts of problems with data - which cause real headaches when it comes to upgrade, never mind placing in doubt every report / enquiry / routing you run on a daily basis.
eConnect understands and obeys the basic GP business logic and creates transactions etc. the same as if they were manually entered.
My advice would be to upgrade your GP software and invest in eConnect.
Best regards,
Ian.