I can understand keeping things simple.

I have no idea about Fanuc values, but I know there are people who buy machines just to get the control, then scrap the machine.

Nema34 is 69.58 square distance between mounting holes, and 86 overall square.
Those servos are not actually that powerful. 112V and 1A puts them at 120W continuous (there will likely be an instantaneous rating 2-3x this).

Kinco from Zapp, you could go for SMH60 400W servos which are £264 along with a CD422 drive at £240 makes it £504 per axis (those prices are including VAT).
If you go for a Chinese option, 200W servo and drive combos can be had $264 per set (https://www.aliexpress.com/item/New-...760383887.html) or 400W for a similar price (https://www.aliexpress.com/store/pro...760376015.html with an 80 frame motor, or https://www.aliexpress.com/store/pro...760394727.html with 60 frame motor)

Or I've just remembered CNCdrive do servos and drives. They do AC servos in 156 and 400W versions at €156 and €198 respectively, although I can't find their corresponding drive in their web shop. They also do DC brushed servos, but I'd personally pay the extra for AC servos.