I do this a lot on all my fleet of old singles, Maas, vespoli, janousek, kaschper, pococks, etc.
footboard plates: typically the boats that I've worked on redoing track screw holes have a little extra room on the mounting platforms so sometimes I've just filled the holes and shifted the plates slightly fore or aft. yes a cheat. If I know I'll have really big people in it, I'll shift aft, or if it's a boat really small people will end up rowing shift to bow.
for filling whether I reuse or shift I'll trim some small shavings of tongue depressor. I use a tube of thickened epoxy (stirred in some microballs), put a little into the hole, then stuff the hole with some of the splinters such that they hold themselves in place, then fill the rest of the way with the epoxy. Some boats have very thick mounting plates, some less thick that the holes are worn through such that epoxy you put into the hole will drop through to the bottom of the boat. I use a very thin long nail to probe to see if I have a bottom or not and tells me if I can fill it deep or just construct it. After it hardens, there may be a bump of extra wood or an epoxy bede to sand. Then drill, either shifting the plates a little or no, both plates that is.
If I have a footboard plate screw strip and this boat is in daily use and need to get through another couple weeks until I can take it apart, dry it out and do properly, I'll simply take some of the tongue depressor splinters, shove them into the hole until tight, then screw in a slightly thicker or longer screw with the right head.
tracks: If your boat builder didn't have grommets I would find some from another builder. It will make your future much better. Typically the hole in the deck where the grommet mounts enlarges. In boats where there is no grommet, the hole enlarges, and the underside of the deck gets all chewed up. This way, when you end up screwing the tracks down tight you're compressing against the plastic grommet and not crushing into the honeycomb.
Make a paste of epoxy and microfiller again, I would take a piece of masking tape and attach to a piece of wax paper or plastic food baggie, then tape that on the underside of the hole. sand what you can underneath and wipe so the tape has a good grip. then fill, dry, pull the tape off the bottom and drill.
mount the grommets with some marine caulk. I've seen some boats where manufacturers don't do this, prolly not necessary if your deck is not honeycomb.
Don't know if this is the ideal ways but it's been successful for years for me, I like putting my repair techniques out there so better craftsmen than I can show better ways. The wood splinter fill is something I devised because no fill I ever used ever gave screws a good bite.