In all fairness to the O.P., I *kind* of know what he means.
I've used Pelican for buying parts for my wife's Mini Cooper and, frankly, it IS hard to find some parts. Take the PDC, or parking distance control sensor, for example. I didn't know the part number so I searched for "pdc". I got a result for a mercedes benz part. Search "PDC sensor". I get a result for knock sensors. Search "parking sensor" and I got results for parking brake cables. Okay, search doesn't work without a P/N. Surely I can browse for it. So I browse Electrical, and would expect to find it under the Sensors category. Nope. I never did find it this way.
I finally found a website that has the OEM diagrams, similar to the PET we use for our P cars. From there I was able to get the part number. With the part number in hand the search was easy. But searching for a description on here is pretty useless.
OP, here are a couple direct links to various PETs - you didn't specify a year:
Here is '70-'73
Here is '74-'77
I picked these based on the dates in your signature.