You glue the block onto the tang and grind/file/sand it to dead straight. it isn't rocket science
That way, you also can adjust the handle as you go to fit the blade in length and size.
Additionally, you need to make a handle glue-up clamp. It is two long pieces of 1/4" threaded rod ,four 1/4" nuts, six 1/4" washers, and two wing nuts. Make two slats of wood about 4X1X1 and drill 17/64" holes about 3/4" from the ends so they go on the rods. With the slats together on the rods, drill a 1/4" hole through both slats exactly in the center. Use the nuts and washers to permanently attach one slat near the end of the rods. Slip the other slat on and put on the other washers and wing nuts. You can now adjust the nuts to apply pressure on the handle holding it snugly against the blade/guard while you adjust the handle so it lines up straight .. and let it cure while clamped straight.
In use, place the tip in the center hole of one slat and put the butt near the center of the other. Snug down the wing nuts, moving the handle and angling the slat as needed to hold everything straight. Dry fit it a couple times before doing it with the epoxy in the tang hole. Use 24 hour epoxy to allow plenty of time for clean up and adjustments before it sets.
These are also the right tool for the job in making stacked or multi-piece handes
Here are some examples in use.
https://video.search.yahoo.com/sear...2beca4c463b9c994fbe1e6c0f5a047b0&action=click
https://video.search.yahoo.com/sear...=5eaf85dbafe8db07a26e022669f0d1ed&action=view