That crankshaft is finished. You need to replace the crankshaft or replace the engine. My first question would be directed to Deejay, and I'd ask him whether there is any difference between SB45s fitted with Tecumseh and B&S engines. If there is no difference, you could fit an old Briggs 60102 and have an original engine that happens, as a bonus, to be incomparably better than that woeful Tecumseh. (I had a Tecumseh of that vintage for a long time, and built up a strong dislike.)
If the Briggs engine would be considered non-genuine by the purists, you'd have to choose between getting another Tecumseh from a wrecked mower, or abandoning originality. I suspect you'd still end up with a 60102 - I don't see the Honda having any advantages, if the rumours of loss of quality in recent times are accurate.
