I used Mobilfluid 424 (which has since been renamed to Delvac) in my 3725 and it worked fine. I would have used it for my last change but TSC wasn't carrying it then and the price was high. I ended up using Duragard. I'd probably use Delvac if I changed the fluid today.
When I was looking for fluids I checked the specs of the oils recommended by Branson, mostly the low and high temp viscosity, and the 424 was close for both.
One drawback of the 424 is that it's clear, so it's tough to see in the sight glass if the level is above the glass. The Duragard is tinted. But if you fill slowly and keep an eye on the glass its not an issue. I use a bucket pump which is really slow but safe.