I used to have a Custom Weld. You can check their website for weights, and they can give you the trailer weights as well. I believe mine held 50 gallons, but I can't remember. The V-8s are heavy. I want to say my 20 ft weight was closer to 4000, but again, Custom Weld can give you numbers for their boarts. Most of the v8s are going to be nearly the same weight with a few having shorter sides and thinner metal.
Keep in mind the Hells Canyon manufacturers tend to make boats with a longer bow that will handle water hitting it which is good for waves as well. Most of the Oregon boats are more weight forward in the front with a less strong windshield. On smaller rivers, those are better since the balance the weight more forward.
Since you are in Oregon, I'd also check with the guys at ifish or at least search there.