Dan,
Welcome on board.
Gardner enthusists in the UK will have all the info you want.
Boatdiesel also have some drawings and info but there is a $25.00 joining fee for 12 months.
Roberts Hall ltd are your source of Gardner mnuals.
Joe Mcool in Ireland is also another good Gardner man in the UK.
Although he did have his business up for sale recently.
I recently put a 6LXB into my boat as a replacement for an old Fiat 8210.
More than happy with the transplant.
When Gardners finnished up it was a sad day in small marine engine world.
Cheers
Benn