You dont have to but a peice of 7/8" .049 will slide right over that 3/4" peice so you can still turn it. Also consider another brace in the lower bars if you dont put the upper brace in.
Your looking at about 20 hp difference. Shitya!
As long as it is jetted properly it will not hurt reliability but consider having the crank trued and welded to keep Iit from separating.