I always enjoy watching your videos.  I repair mowers, snowblowers and 2 cycle engines in my driveway for neighbors and friends.  Watching you repair equipment is enjoyable because it is a journey of learning and discovery, similar to my experiences.

I know most Craftsman equipment is made by MTD or sometimes AYP.  I may be wrong but that mower seems very similar to a Toro right down to the belt pulley/blade adapter.  Even the tread pattern on the wheels and the spring loaded pawl is Toro typical.  Possibly Craftsman rear wheel drive option had to be made by Toro.  Maybe MTD doesn't offer rear wheel drive.

Yeah!  Not only is it good to see you back, but this is almost identical to my mower that has been running for something like thirty years.  It started smoking, but that might be because I had not changed the oil in about 15 years!  Ha ha... very cool to have this video as a document if I need to pull this engine apart.  Nice!

Worn out Briggs Quantum engines smoke quite a bit. I "solved" it with 20W-50 oil and Engine Restore CSL in the silver can at Walmart.

Nice job!
One other thing that can cause smoking is a bad head gasket, although I don't know how likely that would be on one of these flathead engines.

if you are going to make life difficult for the next guy by using RTV then just throw the gasket out, its useless and you are messing with the endplay clearance in the engine.  Hammering on the sump to put it back on is a big NO, it should slide on and fit without any difficulty, but nontheless you damaged the oil seal by sliding it back on OVER the rusted shaft.    You redo the lower end and dont even touch the valves?   You are right there, do the valves.

you are young and learning but man.   Those engine mount through bolts would have come out easily, should not have touched a drill bit.   clean the rust off the crankshaft before removing sump cover, it will save the oil seal and be easier to remove.  Remove the crankshaft when you hone.   its called crosshatches for a reason.   You didnt measure the ring gaps before installing, thats a HUGE missed step

haha came to actually watch the video and then i realized the name is very similar