I don't have a service manual on this, but I found a link to B&S tools online. I would think your guy could get it done if he is an experienced machinist- tho I understand the wanting of the spec as well. Moral of the story- the tool cat doesn't show anything other than the reamer etc part #s. Maybe an older servicing dealer in your area would do it or borrow the tool to your guy. I know they don't come cheap to buy. good luck with your rebuild. Here is a link that might be useful: B&S tool cat

RC is right here although Kohler and others recommended not using api service SM due to the zinc reduction. I have never seen an engine fail that had the proper quantity of oil in it.

What happens if you tighten the dipstick just enough to seat it, without going that little bit further? Now that I finally know the nature of your dipstick and the fill tube, I guess that the dipstick tube once had "stops" to tighten the dipstick cap against, and they have long since wore out or broke off. If that turns out to be the case, and you like the convenience of the dipstick enough to buy a new one, they might be available from Briggs. Your dilemma is certainly not the usual fair for this forum, just a bit rare (has this EVER been posted before?). But, in the end, the dipstick & tube might have been "a Sears exclusive" that Sears specified for that genre of engines back then. The cap needs to be in place and tight to assure the engine crankcase breathes through the OEM breather instead of to open atmosphere. The "breathing" of the engine is a series of alternating "inhale-exhale" events. That means if the "INHALE" portions of the process are through an unfiltered atmosperic source, dust can be drawn into the engine with every stroke of the piston (this would be the underside of the piston doing this in the crankcase, not the topside of the piston in the combustion chamber). So, if the cap does not seal tightly, that is a source of dirt for the engine to eat. And then there is always the chance the cap could be vibrated off ande lost.

I'll try to answer some of this, but I am "supposing" on the differences between the T-K module for Tecumseh engines and the B module for Briggs and Wisconsin engines. My "guesses" of why there are 2 different modules could be listed as follows. (1) Possibly a significant difference in the potential voltages in the primary circuit of the different brands magnetos. (2) Possibly a difference in the "cranking RPM value", or the low idle RPM value, between the brands. For the module to be effective for Snapper's intents, it must be able to distinguish "cranking RPM" from "running RPM" or it is useless. Tecumseh and Briggs both seem to fail in offering any kind of "low idle RPM value" and instead refer you to "check with the equipment manufacturer", but Snapper fails to give it as well. Snapper is "evasive" about the reason and only states that "if the wrong module is used, it will DEFEAT the purpose of the interlock system. They state only that the engines will start with the wrong module in place, not how/why that happens. Why just 17 HP? pjb found the engine at a yard sale for short money.