The heater in my 725, was not original. It is a belkamp model. It’s a small 13k btu model. To make a long process short, summit racing has a 2.5 diameter hose set for sale, total should be around 40$. I ordered the 7x.5 model, although the duct length is longer in the 725, it works. The one thing summit doesn’t offer is a way to attach it to the belkamp. That can be found at
https://nostalgicac.com/defrost-difu...sh-grille.html. They have an adapter that works for a 2” hole.the also have all the products needed to ramp up to the 2.5 for the ducts.
Anyway, it all bolts, screws, zip ties in fast, and works