Here's a NO pressure switch. You didn't say what year you need it for but if up to 55 you may as well use the original, they work really well.
http://www.oldchevytrucks.com/cart/product.asp?prodid=EL106&i=9766|||||


1951 GMC 250 in the Project Journals
1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-