I'd aim for servo's similar power wise to what was fitted, as too big has the potential to do a lot of damage if things go wrong. I got told from a very reliable source that those interacts will handle the original servos running the axis into the end stop without doing any damage, if something does go wrong.

Plus you want inertia to match somewhat, as too big an imbalance can cause tuning problems. I was advised 110 would be better for my Shizouka which is a couple hundred kilos heavier than a Bridgeport.

One thing to be aware of with the cheap Chinese servos, is they use mains voltage for control power, so if mains power gets cut i.e. due to an e-stop, you've lost position. It's not the end of the world, but one of the things I like about my lathe is the position never gets lost during an e-stop, as the encoders are permanently live.
If you want a copy of the BST servo manual, drop me a message, and I'll email it over.



Oh, and is this a potential replacement for Thor, or are you just wanting to burn a few more KW to help keep the workshop warm? :-)