As long as the cabinet does not rock, bolting down is probably not needed.
What is important, especially with a Myford, is to ensure that the bed is not twisted. The level from Headstock to Tailstock is less important, unless you are using flood coolant, but a twisted bed will result in taper turning.
The time spent in ensuring that the bed is not twisted is not wasted. Sometimes the last delicate adjustment can be made by changing the torque on the bolts that hold down the lathe bed.
With riser blocks, this adjustment is much simpler, but there are ways of levelling without riser blocks.
Howard.