Side rails have nails that have a very coarse thread machined into them. Carefully protect metal surface of side rail and gently pry up nail head just enough to get a plier on them and then you can basically unscrew them. Its only a couple turns to back out the entire nail.

If you damage surface its easy to repair with sand paper and then regrain using 3M scotch guard or finer sand paper but if rails are really clean its of course better to work carefully in the first place.

Lock down should not be nailed- at least is not in 1973 and 1976 examples I have worked on. Your just missing a screw or possibly need to apply a bit more force. It should basically lift straight up- caution!!! You need to remove the locking mech that holds down play field before the bar will come out!! <if I recall correctly> Carefully inspect both sides to be sure you have all the screws out then if it looks like you do need to remove the lock, unscrew this and remove and THEN attempt to gently pry it up and out.

Nothing hidden here- look around very carefully to be sure you have it all unscrewed and your good to go. It could easily be "glued" down from old beer/soda/crap and just need a bit of a pop to release it.

You can get new nails from PBR! You will almost certainly need to replace them- its probably possible to remove and reuse but I just replace them.

There may also be a couple nuts in holes which hold the door frame and the lock rec?? just a guess

https://pinside.com/pinball/forum/topic/removing-em-side-rails

Remove all the flush-mount wood screws that hold it in (these are all on the inside cabinet side, about six of them), then lift it up and away from the cabinet. There are only those screws holding it in.

There is qty 6, you missed a couple...