No pump means your bike was made early in the year. I think later ones had a pump.
Yes, you can see from your chart that the needle jet (located in the carb throat) is an O6 on the '76 model and O5 on the 78 model. This means it is slightly smaller on your model, but you have the same needles. So you would get less gas through the main jet in all throttle positions because gas flow in this circuit is limited by the size of the needle jet. You could attempt to increase flow by raising your jet needle one position. You would know right away by taking the bike on the highway and cracking the throttle wide open. If that doesn't work you could change out the needle jets...not a difficult job but you would need to find some O6 jets.