I'm not finding the part you're looking for, so I bet it'd be a tough replacement.
Looking at it, there are a couple of options for you. First, you can buy two single sided connectors, like this:
Using two of them, you can place it onto your sensor and connect it to the existing wiring harness.
You could always dismantle these by taking the contacts out of them and putting them into the body of your original plug. I believe if you use a very thin flat-tipped screwdriver, you can get the contact to release inside the body. Slide it up between the body and the contact all the way to the base and I'm pretty sure it will release. I'm not sure which side of the contact you'd need to work on, or which way it would come out (the wire side or the connector side), but the thing has to go together somehow, which means it will come apart. I believe I've done this before to the same time of connection (IIRC, I had a melted connector and took the wires out). Just play with it some and you can probably work it out without too much of a hassle.
An even easier fix may be to just get some female bladed terminal ends which would slide down onto the blades of the sensor. Connect these to your wires and you're in business.
EDIT: FOUND IT!
PN:34621 TEMPERATURE SENDING UNIT LEAD REPAIR KIT, for 2 flat blade terminal type sending units
You'll have to drill down a bit to find it from the page. They have some markup on the page which shows as you click, but doesn't do anything with the URL. How you want to drill down in the catalog is as follows:
- Click on Automotive Switches from the main page
- Click on View Catalog / Order Online under any of the subsections
- Click on Make/Model/Year of Vehicle
- Click on GM OLDSMOBILE FULLSIZE
- Enter year, then click Display Catalog
- Scroll down to find the subsection entitled REPAIR COMPONENTS (for wire harnesses)
The part is listed there as shown above. As of this post, price is $17 (plus shipping I assume). Here is a picture of what you get: