No. You MUST get it balanced. Internally balanced mean that you do not need a special flywheel/flexplate and harmonic damper to achieve balance. Factory SBC400's had additional weights on these components to make this work. Internally or externally balanced rotating assemblies both need to be balanced, the difference is how it is achieved. It is two different styles/methods.
You can get this kit but you must:
1) have it balanced
2) buy a new flywheel/flexplate for internally/neutral balanced SBC's, like a SBC350 . Aside from the fact of the balance issue, the link you posted uses a 1 piece rear main seal, which uses a different crank so you old flywheel will not even come close to physically bolting on.
3) buy a new harmonic damper for internally/neutral balanced SBC's, like a SBC350