I've been eyeballing these for a long time since for my DIY carb tuning efforts this would be a great data point to have.

What I've learned so far is this: while the well known aftermarket vendors for the most part can provide you with a nearly "bolt-on" setup, unless you have to do so I would recommend eBag shopping...most of these sensors are pretty generic and they can be had for literally $10-15...so if you have to make your own mounting brackets it just makes sense to save a boat-load of cash in taking that approach.

Search eBay for the following item ID 156108911635, it literally appears to be the very same switch: 'GM part # 17112679 TPS'.