Assuming it is a 450 from the info you have, it is a 7450 series loader. During those years the crawler itself and the loader attachments each had their own parts catalog. The parts catalog is available on line at jdparts. Here is a link to the 7450 series loaders:
https://partscatalog.deere.com/jdrc/nav ... ment/65555 . You can get the John Deere part number for the seal kit from the parts catalog and use that to narrow your search. One seal kit is shown for a boom cylinder in the parts catalog I posted the link for. Several different kits are shown in the parts catalogs for models after the 450 Loader. Lavoy sells parts, you might contact him via email:
postmaster@jdcrawlers.com, to see if he can supply a kit. His business provides this site for our use.
The serial number for 450 crawlers and early 450Bs is on the panel below the seat, about behind the operator's right calf when setting in the seat. Later 450Bs, and 450 series after that, had the crawler serial number tag on the front panel of the battery box. Some 450 loaders had a tag for the loader itself, to the right of the crawler's instrument panel.