I just put in a stainless sink in my 73 boler. They do have a sink at home depot that is almost the exact size that we are looking for in the boler. However, it is about 1/2 inch smaller in length than the one in the boler. I bit the bullet and put it in anways, there are only two small gaps where the flange isn't able to cover the existing cut out. I was going to put a piece of aluminum flatbar, or cut out an insert to fit the shape of the sink and extend the flange but i decided it was too much work. I just filled the holes with silicone for now until i figure out what to do with it at a later date.
The last two pictures in the album show the kitchen sink with the two small gaps on the left hand side and how it looks. I admit it isn't a perfect fit but as hard as i tried at my local dealers, they just weren't able to order in a sink that was the right size.
I just recently took my vent out because of a poor seal. I was able to find the new chain at canadian tire as well as other places that have lighting
supplies. If the vent is not overly damaged, there is a good chance you can take it out and repair it quite easily.
Your trailer looks very nice!
Best of luck.