My friends shop had the RPC and he found the step down transformer surplus for cheap. If it was easy to do, I would have kept the press. I don't know if you could drive the step down xfrmr directly with a VFD. I think if you talked to someone who you were buying the VFD from you could ask? I had good help from Automation Direct when I needed support. Honestly, I don't feel confident that would work since the impedance of the transformer isn't only different from the motor but there is a damped coupling electrically speaking. Another pitfal is that you will need to limit the frequency to the 60hz position to keep the transformer working correctly. Since you have a geared head drill, I see no real reason to try variable speed anyhow.
im sure there are people around a lot smarter and more knowledgeable than I. I hope this helps you.