As Carps can tell you manufacturers don't like to design new parts if they don't have to. It's too expensive. Besides how many different wheel bearings can Timken, or Toyo, design that are intended for a car that weighs between 3000 and 4000 pounds, and is intended to be driven on fairly smooth roads, at about 60 mph. So for economic reasons the bearings are the same from make to make. Even foreign cars use the same bearings in a lot of cases. Remember Timken has plants all over the world. If you start converting some of the odd ball bearing sizes to metric they make a lot more sense. So the best thing you can do is obtain, by means legal or nefarious, a bearing specification catalog. Measure your ID, measure your OD, and check what is available. If by some chance what you are doing is REAL odd ball, sometimes by turning the hub out a few thousandths you can find a bearing that fits.
Seals are the same way, but there are not as many available. By the way, industrial bearing supply houses have seals that auto stores don't list. If it's good for a lathe shaft at 3000rpm, it will work great on your wheel. Sometimes you have to turn the seal seat out, and sometimes you have to make a spacer ring, and JB weld it in place. If the spindle is too long you can make a spacer the same size as the seal for the hub, and kill two birds with one stone. If the spindle is too short, you can use a thinner nut if it isn't too much, or depending on the hub, it is sometimes possible to sink the outer bearing deeper into the hub. Be careful with this as some hubs are larger in diameter in the middle. In that case you can sometimes find a bearing with a slightly larger OD to solve the problem.
Caliper brackets are generally a plate to fit the spindle, and one to fit the caliper. Sometimes you are lucky and the plates are on the same plane, most of the time they aren't. So make two plates, jig them and weld them up. Tips from my experience allow for bleeders, and brake lines when you do this. Don't ask why, just trust me.
Being an expert means you made all the mistakes in private. I remember my first trick suspension, when I took it off the jacks, it went all the way to the floor. Live and learn. The next one on that car looked the same but fixed all the mistakes I made the first time, I made new ones.
Drive shafts are another area that is like this. Spicer, and Precision make adapter u-joints that are available everywhere. They are a little more expensive, but much cheaper than having a drive shaft made. Unless its really short, or really long you can usually find one in a salvage yard that will fit, with the right adapter u-joint.The other advantage to this, is when you blow the drive shaft out the side of the car showing off, any salvage yard has a gremlin drive shaft in the corner somewhere. Also Ford,GM, Mopar,and AMC all had different yokes for the trans and rear ends. a good salvage yard guy can tell you if Hudson had a 1" longer yoke on the rear end so you can use that Valiant drive shaft that is an inch short. Every car guy needs a good Junkie.
I'm lucky to have a big old barn,so I will take any old car that comes my way. my two boys know what I usually keep,so they "scrap the caddy clyde" for me. amazing how fast they can strip a car. I pay my grandson a couple of bucks to take out screws, ect. Everything gets stashed in boxes in the barn.that saves a lot of trips to the salvage yard. You never know when that Ford six alternator bracket turned upside down and backwards comes in handy to mount a Mopar power steering pump on a Caddy.
Taking cars apart lets you know how different manufacturers solved problems, and you can use these ideas on your ride.