The tinternet is your friend here for a starting point at least but I would take all info with a pinch of salt as no two engine set ups are the same due to carbs,cams,head,exhaust manifold etc.
This is what a 10 second search on Google came up with.
Jetting
http://7faq.com/owbase/ow.asp?HowDoI...erCarburettors
parts
http://www.fuelsystem.co.uk/weber%20jets.pdf