Under the old rating system which credited your 91202 engine with 3.5 horsepower, the 106232 would be rated at about 6 horsepower. This is due to its larger capacity, higher compression ratio and OHV design. (In reality both engines have far less power than that as-installed on a mower, but it gives a realistic idea of one versus the other.) I regard it as a somewhat oversized, overpowered engine for your SB45. If it conforms to the standard small-engine mounting dimensions, which Briggs engines normally do, it should fit fairly easily onto your mower as a direct replacement for the 91202. Aside from being rather larger than necessary and an Intek engine, it seems to have a good specification, and would probably do your job quite well. I generally lack enthusiasm for Intek engines, because of what I see as significant design errors made in the larger ones, but those issues do not apply to the 750 series. Also, the 750 is likely to be substantially smoother-running and more fuel-efficient than your 91202.
I personally regard the Honda GX120 as both a better engine, and a more suitably sized one, for the SB45 compared with the Briggs 750. However as some American said many years ago, "Opinions are like backsides: everybody has one." I do not know your reason for choosing such a large engine (160 cc and 6 hp, versus the Honda's 120 cc and 4 hp), and it may be a very good reason for all I know. In general Briggs engines cost less than Hondas, and as the world's largest manufacturer of small engines, Briggs obviously must be doing something right.
The usual crankshaft extension diameter for the GX120 is 3/4", the same as the 91202. Note also that matching engine-side clutch-halves of both 5/8" and 3/4" for the SB45 are available as spare parts.
