Not only can many different part options fit the same vehicle, but a given part can fit more than one vehicle--which is a many to may relationship:
What you have is pretty close to what you need here, though it can be a challenge to figure out if you need separate tables for different parts or a combined table of all parts. I'd recommend the combined table if at all possible. "Detail" tables for specific part types can be linked in to that combined table if they are needed. On the other hand, maybe brakes and parts are the only type of parts the business needs to track and then separate tables may work out just fine.
A portal to Model_Part placed on the Models layout can list all parts for that Model. You can also place several different portals to Model_Part on the layout and use a portal filter to fliter the list to just the OEM parts. (or just a type of part like Tires...) These filtered portals can be static--they alway show a specific set of parts or you can set them up so that you can select for specific sets of parts that fit the given vehicle.
Thanks for the encouragement. I want to make this database easy to update as items are changed or more are added.
What I hope to do is "hook" several similar parts to one OEM part. In other words be able to choose and show many alternates to the OEM part, but just have to relate them just once. The tire table has many brands and styles that will work on a selected model vehicle.
So if I choose model 1 I see the OEM tires, but also other tires that will fit too. How can I do this in the proper relation way?
Make linking records in Model_Part for both the OEM and Non OEM tires. Use a field in Model_Part to designate which parts are OEM. (I am assuming a part that is OEM for one vehicle is not for another.)
A portal to Model_Part will then list both OEM and non-OEM parts. YOu can also set up two portals where a portal filter keeps the OEM parts in one portal and the non-OEM in the other.
I'm going to set it up per your suggestions and see what kind of layouts I can come up with. I am a rookie at Filemaker, used Access for many years. It's cool to experiment with the added features this program offers.
Thanks for all the insight and encouragement.