Wing Incidence
Arlie -
If you are referring to SK-51 Setting Wing Incidence Level, the 2.8" block sitting on the aft spar "sets" the wing incidence to 1/2*+ to the fuselage when the level that spans the two spars is indicating level.
As noted above, if you can't get the design incidence (for whatever reason), you can fudge a bit one way or the other. But if the F-404 bulkhead (spar carry through) was installed correctly, it is also at 1/2*+, and aligning the wing at some other incidence introduces torsional stress in the main spar at the wing root where it enters the fuselage.
The Horizontal Stab is set at 0* to the fuselage, as shown in SK-48 Leveling of Horizontal Stabilizer. So the stab is set at 1/2*- to the wing. I don't know how old your airframe is, but, if checked, you might find the stab set at the wing incidence or slightly above. Way back when, John Harmon recommended to local builders to shim the stab to wing incidence - before internet, so we all got updates by word of mouth.
As Vern says, as long as the incidences are in their correct relative position AND not too much torsional correction is required you will probably be fine. Your fuselage will "fly" at a slightly different angle than designed, but most likely will be unnoticeable.
David Howe
HR II S/N 002