This older thread
Dipstick and Tube info was started about 261's, but is the same for 235's according to the Chevy Master Parts Books and is good info to start with to answer your question.
Some further searching through later Chevy Master Parts books provides the below snap shot info showing the gauge stick and measuring points, the gauge measurement dimensions according to the diagram and the oil gauge tube dimensions (marked in red for your application - guessing your 1955 235 is a 2nd Series?).
As far as sourcing what you need, post an ad in
Truck Parts Wanted or grab your tape measure and see what you might find in local salvage yards. Since they are both for trucks and passenger cars, you might just get lucky.
