7.25 axle splines

I don't want to drill. there is too little material left. I think the only thing left for me is to swap the cage of the 4 inch axle into the 4.5 inch axle. then replace the inner gears of the cage with the setup from richmond, which fits my splines on the larger axle. I'll let you know if that worked. many thanks for your help. I'm always happy to receive further tips. If anyone knows where I can order a cage for the 7.25 axle with a 4.5 inch bolt circle in America, I would be very happy about a link. Nothing ventured nothing gained. sorry for my bad english.