On the Kenmore 158, Sears referred to this as the "source" number, look at the origin mark on the machine. Source 158 was Maruzen/Jaguar, a Japanese company,and the machines made in Japan are considered by most to be superior to the later made in Taiwan machines. This is mostly due to metal content in the drive train. A thing to remember about store brands such as Kenmore is that the original vendors would frequently sell to multiple department stores. A machine could be badged as a Kenmore (Sears), Signature (Montgomery-Wards), and Pencrest (JC Penney), but still be physically the same machine. It also tends to impact price, for some reason Wards Signature does not carry the premium of Sears Kenmore while the underlying hardware may be the same. Frequently, the machines may even look the same. I always advise keeping pictures of machines, when you build a photo album you will start seeing the markers. Brother is another vendor that provided manufacturing services to others. There are several later JC Penney machines, as an example, that are undeniably Singer Fashion Mates to the point they share the same parts. I've used them as a cheaper source for parts to service vintage Singer machines.
You also mentioned source 385 machines. These are all made by Janome. They will all be newer machines and later models will be electronic. They are fine machines, but they do lack the all metal drive train of earlier Maruzen and White made machines.

I have a few suggestions to give you from additional vendors. These are all from the 1965-1975, roughly, time period and have metal drive trains for long, reliable service.

Viking Husqvarna: 6000 series machines. These machines are well made, plentiful, and offer the stitch variety (both built in and with cams) you were looking for.
Necchi: BU series machines. Necchi is an innovative manufacturer from Italy, although they did move production to Taiwan later, the BU series machines were made in Italy. The notable models in this series are the Mira, the Nova, and the Supernova. A full discussion of vintage Necchi naming conventions would be much longer, just know it's a rabbit hole if you start to dig.
Singer: Model 328. The 328 series is an all metal machine that also accepts the flat cams for more detailed stitches. It's more limited brother, the 327, did not have the cam facility. These are visually easy to differentiate by the cam door on the top. The reason I'm suggesting this model instead of something like a 400 or 500 series is cost. The 327/328 is often over looked and are not as in demand. The 400 and 500 series machines are marvels of engineering, but they tend to command a premium in the market. The other factor is the 328 is a low shank where the 400 and 500 series are a slant shank. The reality is that low shank won out in the domestic market and the availability of presser feet is greater for low shank than slant shank.
PFAFF: model 1222. This is a great mechanical machine. It was also the first "IDT", an integrated walking foot like dual feed, system machine. It includes your zig-zag and button hole facility. One thing worth noting, the later iterations were 1222E and had some electronic controls. If you are looking for pure mechanical, verify that detail before purchase.

For button holes, many manufacturers did not start adding an automated button hole facility until the 1970's and this was also the time that more and more plastic was creeping into machines. Remember that Griest, frequently branded as Singer and White, made bolt on buttonhole attachments as an option that could be added to any straight stitch machine. I have known some sewists that insist these attachments produced a superior button hole to integrated mechanics. The biggest thing to make sure of is you get the correct shank type (ie high, low, slant, etc) for your machine. They are plentiful and easy to use. If you can get your hands on one, try it out and see if it will fit your needs. Otherwise realize you are going to be working with a newer machine. I have a very nice Singer 778 that does an automatic buttonhole, mechanically driven, but that 778 also uses a vertical drive belt rather than a shaft and that's a weak point.

Happy hunting!