I mean this is basic poker 101 stuff folks. When someone puts in nearly 20% of the effective stack and you are out of position its very tough to play any hands by just calling (other than like QQ+).
On the other hand its very easy to just 4-bet all in. But since he's a tough aggressive reg, we can't just stick it in with legit hands (JJ+ AK), or we get exploited a ridiculous amount.
We need a bluff frequency. Since the most common hand in his range is AK, we should choose hands that fare best vs AK to build our bluff frequency. Pocket pairs are the obvious choice. But we don't necessarily want to shove every one of them or then we can be easily readjusted to which is no good. So just randomize by shoving the 3 best ones, 88-TT. Easy game.