And to the OP, the studs should be a loose sliding fit in the raiser blocks/jackscrews.
Yours are probably locked in by crud and paint. Use the stud nuts, fit two together on each stud and lock them together, and you should be able to break the seal and get the studs out by twisting the nuts/studs with a spanner.
When you refit them, here's a dodge to make the process, and that of levelling, MUCH easier.
Source four extra 5/16 BSF nuts, even better if you can get half nuts.
Fit the jackscrews to the raiser blocks, and screw them in to the raiser blocks fully, then unscrew them around 2 to 3mm each, no more. Ideally then check the total height of each raiser block and jackscrew with a digital caliper, and make them all the same.
Fit one (half) nut to the (longer) threaded end of the studs, and screw it right to the end of the thread – loose, NOT locked. Drop this through the jackscrew and raiser block, and through the tray and stand. Loose fit the whole assembly with a nut under the stand.
Repeat with all four, and you should have four studs protruding from the blocks, that you can lower the lathe on to.
If you don't fit the extra nut, you have a lot of faffing trying to locate the holes in the stand/tray/raiser block/lathe bed, whereas if you do fit the extra nut, the lathe drops straight on to the protruding studs.
There should be just enough length in the studs to accommodate the extra nut.
When you start levelling the lathe (following the Myford instructions), nip the two top nuts (either side of the lathe bed) up against each other, and make sure the nut under the inside of the stand is left loose, until you have finished levelling, then nip those up last.
The other advantage with this method is that it gives you a bit more space in the gap between the raiser block and lathe bed to get the jackscrew adjusting spanner in when you are adjusting the jackscrews.