likely they will all fit...
they are pretty standard sizing...
any unit that old, the vent cover was probably deteriorated anyway
the standard 14 inch cover is what you probably had... I would also install on top of that cover a Maxxaire vent cover that will go over the vent cover and provide additional protection in case of rain... in other words, the vent cover needs to be closed to prevent rain from coming in, but with the Maxxaire on top, you can still keep the cover open in hot humid weather...
try amazon search Maxxaire
“Too much of anything is bad, but too much good whiskey is barely enough.
” – Mark Twain
2014 Shamrock 183
2014 RAM 1500 Bighorn Crew Cab, HEMI, 3.21 gears, 8 Spd, 4X4 TST TPMS