Rough shifting 4-speed?

[TwoFiftyShifter]

My 87 K20 has the SM465 behind a 350tbi and 12" clutch. A pretty beefy setup and a heavy truck trans, but is it supposed to be such a bear to shift?
You can never be in neutral and go to creeper or reverse without tons of grinding, but going from 2-3-4 to one of those is fine. When rolling, you cant bring it down to 2nd without being in 3rd, or pulling down hard. and sometime downshifting from 4th to 3rd at 35ish mph takes a hard push. The reason I ask is our severly trahsed 72 plowtruck with the same tranny is alot easier to shift....