Multiple table occurrences is definitely what you need. You might consider this approach to organizing them, called "Anchor Buoy", that makes a lot of sense to me:
One very big question: Why do you have a different layout for every part? At least that's how I read your description. That approach complicates the overall function of your system here.
No every part has the same layout - I just want that one layout to contain like 3 or 4 portals that go to other layouts (in BOMs, Quotes, POs, etc) that display that part on their portals - I;ve been doing this via multiple occurences of a line items table, but maybe thats not the best way? Ill check that link out, thanks for the prompt response
Sounds like you have a good handle on this.
A button on your portal (or the fields that are in the portal row) can be set up as a button that runs a script. This script can copy data from the portal to a variable or two, switch to the desired layout and then perform a find to bring up your part record on your part layout. Instead of a find, the same can be done using Go To Related Record where specify the portal table occurrence as the "from" table and your parts layout as the layout you want to bring up.