I have an older pair of FJ shoes,I need new spikes but cannot find the right ones,the screws are bigger than replacement screws
By your description I believe you are looking for large plastic thread spikes, I would check online golf retailers for them.
golfspikes.com seems to have them. Miht I recommend you call them first to confirm this. 1-800-203-4428
Look under large thread replacement spikes. FootJoy Classics use small thread.
Go to your local club and ask the locker room staff to fit the spikes so you know which ones you need. They can tell you what they put in and have them use their tools for the first set as it is sometimes hard to get the old ones out and don't strip the threads putting the new ones in.
MASTER GRIP HAS THEM AND ALSO SOME DUNHAM STORES
Ttake the shoes with you to a store. They could probably figure it out.