I'm running Weber 44's on a 1973 2.0L, stock. What is the best jet sizing if I'm trying to get performance but also fuel economy?

I will suggest the obvious first, get 40mm carbs.

Next, the venturi . jets, ftubes all work in a combination, so changing one will quite possibly harm you in performance in another part of the fuel curve.

I will tell you that if you call Aircooled.net and ask them (buy from them also) they have kept track of all venturi/jet combos that work well, and offer to trade parts with you till it works correctly for you.

These guys offer this great service just for buying jets and venturis from them, I think its awesome.

Rich

If you don't already have it, buy this book:
Weber Tech Manual
best $10 you can spend for information about Webers.

Aircooled.net also has some great technical articles relating to jetting
and carb tuning:
Aircooled Technicle Articles

Also, if you search this forum, you'll find several threads on jetting.
Jake Raby has commented many times the subject. Search for the threads
that he has posted to.
Here is just one of many that are out there:
44 vs 40 IDF jetting

Hope that helps.

--- bill