Forget casting, as mentioned above…..more problems than it’s worth.
A hand forging is a good way forward, at least you will get some of the grainflow going in the right directions.
If you have them hogged out from solid billet, you may want a stress engineer to do some calculations for you, as the dimensions may need beefing up a bit to take account of the grain being wrong. They will be slightly heavier but I don’t suppose that matters to you.
And, somebody somewhere must already be making this stuff.
Send me the part numbers and I will ask my local Spitfire builder (No joke)