Check your owners manual to be sure. You can download older ones from Grady white's site.
On my 2008 305 Express, the main fuel tank leads to the filler located furthest aft.
On my 1988 gulfstream the front fill goes to the front tank and the rear fill goes to the rear. My tank valves are on the port (left) rear just inside the left rear panel door. That is a 232G
model with a engine bracket.