another learning question

What he said. If your recipe calls for lean to me that means 90% or above to me. Thats real beef like sirloin tip or a peeled knuckle. For fat you can use beef fat that you cut off your briskets, ribeye steaks (with the lip on) or pork fat or even pork butt ha enough fat contian that you can us it.

I think what your asking is more of a personal preference, remember that sausages often have up to 30% fat, so if you were planning on using all 80/20 beef your sausage then you would have a 20% fat ratio now  depending on your preference that may or may not be enough fat for your liking, I make sticks and summer sausage  with this same ratio and that is enough fat for me

with the ratio the kit was asking for sounds like they were trying to hit about a 25% fat ratio so 80\20 isnt that far off

remember it's not really the type of meat you make a sausage with, it's the cure and other spices that define a sausage

hope this helped

Depending on what you are making, don't short the fat.

When I started making sausage, I tried low fat and low salt.  Mostly I made feed for the garbage disposer.

Without sufficient fat you will get a dry and crumbly sausage.  Without salt you get a bland sausage. The term sausage originated from "sal" which means salt.

Good luck and good smoking.