I can only shift from 1st to 2nd in our case 580 super k cannot get either 3rd or 4th gear?
My 580 K was like that when I got it. The bolt that holds the shifter lever had backed off and allowed it to wear the mating piece. After taking up the floor pans I used a flat file to reshape the piece and it has worked fine ever since.
Welcome to HEF roger3! Assuming your gear shift comes from the dash & not the floor - there is a detent at the gearshift pivot - these need a little lubrication from time to time. Make sure this is OK.
I had the same problem with my 580sk, turns out there were 2 problems. Previous owner put 3/16" dia. clevis pins in the linkage where it connected to the transmission should be 5/16" creating a lot of slop. However the bigger problem was all the slop and wear in the shifter it's self, the base of the shifter should be a nice square shape to properly engage with the shift selector plates. I had to build it up with weld and machine it back to original specs. Also there are bushings that were worn out in the selector plates, bronze bushings $1.50 ea at the local bearing shop. Once reassembled with all the wear/slop removed it shifts great.