Do you not have your serial number??? There are three possible blade holders. It makes a difference in the angle of the blade and the bolt size. Without the serial number it is a crap shoot.
As for changing the blade holder that is out as the gearbox changed in there and the bottom output shaft/spline is different. The direction of rotation changed in there too. One of the gear cases turn CCW, serial number 70,000-70,499.
Post us your serial number and I can try to help you more. There are several after market suppliers that have blades but I need the JD number to cross them over.
There are four serial number ranges:
0-49400 angled down holder
49401-69999 straight holder
70000-70499 straight holder
70500-up angled down holder
The early serial number with the angled down holder shows a suction blade being available. The newer angled down holder does not show a suction blade being available.
Need the serial number to know what you need.