Given your talking about an engine lift. I’d assume it not anything too heavy. And the mention of 400 machines, I’d be thinking Ron M or H & F
Check it for lifting holes at each end of the bed. But failing that, you can safely lift a lathe by the bed and the spindle. I have this argument with my crane truck guy, but he does this daily. We only argue once every 6 - 7 years when he is moving my gear.
Any half reasonable labourer can figure out how to drop a soft sling through the bed or around the bed, use packing timbers if you have to protect feed & screw rods.
If you’re going to use the spindle as a second leg to your rigging, don’t use the cross web, or web way out near the tailstock. Find the one near the centre of the bed.
If you only lifted by that one leg through the bed, at about the centre distance, the tailstock end will lift first. However if you drop an adjustable second leg to the spindle, it takes bugger all force to re-establish balance.In theory its the difference between the mass of the head stock and the tailstock, plus any offset due to the headstock sitting on dead ways.
Headstock end will always be heavier, but only by a margin of 10 – 20 %. If you have the bulk of the weight hung by one sling over the centre, and bugger all just to accommodate the off balance of the headstock, ifyou happened to calculate it, there will be negligible load on the spindle.
If you’re of the school (Which comes next). That picking up the bed of something within the range of an engine crane, somehow bends the bed, I’m at a total loose to explain that.
I’ve had that demonstrated by my crane truck guy, put a sling about mid span in the bed, I can physically lift the head stock end tobring it back into balance. I’d call that a 100 kg’s or less. A second legdropped back to the spindle doesn’t mean you are lifting anywhere near the fullload of the machine.
That’s totally at odds with if you put your primary strap /sling right down the end where the tail stock would be. That would be 40% load at the head stock, 60% load at the spindle. Avoid that by putting your primary strap about middle of bed, and your secondary strap just as a counter balance you won’t have a problem.