I bought a new cutting edge for my BX a few weeks ago, and decided to add a replaceable cutting edge to the bottom of it. Bought a 48" long one from the local Kubota dealer, I think it was for a later BX or B model, with 7 holes to bolt it to the bucket.
I figured the weld-on cutting edge would be really hard and difficult to drill, but after I located, marked and center punched the 7 mounting holes, and set it up in the drill press. I started with a 1/4" cobalt bit and use lots of lube, and it drilled just about like mild steel. I finished up the holes with a 1/2" cobalt bit, used plenty more lube and it took hardly any pressure to drill them out and the bit was only warm when I finished up.
Now I'm trying to decide if I want to tackle replacing the cutting edge myself or take it to the local Amish welding shop. As reasonable as their prices are, I'm leaning towards taking it over to them.