http://dimequarterly.tierranet.com/
Check out this link. It's for the 510's but tuning a carb pertains to many Datsuns. You will find a selection of catagories on the left side of the page. Scroll down to the "Technical Dept". Then select "Engine".
A page will open up on the right side and then you can select the article on tuning the Weber DGV. Hope this helps.
Good Luck