I'd look at removing the adapter plate and use a mount that replaces the original Ford mount. That will move the box closer to the rail providing more clearance. I've used both Pete & Jakes and Weedetr mounts; but with different engines, so I don't know if it would be the answer in your application; but worth looking into
I am installing 525 Saginaw in my 36 pickup with a 37 engine, block-off plates pumps and 36 exhaust manifolds. I am using the proper Heidts adapter plate. The box hits the exhaust manifold. Anyone have any other suggestions appreciated.
I've used several of the bolt in plates from P&J's and they worked great. They do require removal of the stock mounting plate. It moves the box a little closer to the frame. Remember Heidt's bought their way into the straight axle business, Pete and Jake's have lived the business.
Is there an advantage to adapting a 525 box versus a properly rebuilt 37-48 Ford cross steer box?