Need recommendation for a Carb for better MPG!

you definitely want want with the ability to advance on the tool. As Toolman pointed out, our LA's timing marks only give you 10 degrees and if you want to check total timing in the future, you'll need much more than that. The digital ones are nice as they usually have a built in tach too.
Also, I'll leave it to the 340 experts on the board but you'll probably need more initial timing than what the factory manual calls for due to modern gas blends. My 360 for instance is happiest at around 12 BTDC which is 7 degrees more than what the FSM calls for.
This is the kind of priceless info that I really respect because I would not have your experience. THANK YOU! One thing, could you elaborate more about when you say "you definitely want one with the ability to advance on the tool" what that means? Sorry but I'm trying to learn. If I understand this correctly, are you saying that you can get a digital timing light that will allow you to advance the timing? If so, do you know if the Innova 3568 will do that?