Nathan Young writes:

Isn't there a minimum runway length to have an ILS, like 4000ft?

There might be a minimum but it doesn't appear to be 4000 feet.
VVS, 05, 3458, 100, ASPH-F
HIE, 10, 3495, 75, ASPH-G
PVC, 07, 3500, 100, ASPH-G
FCM, 10R, 3909, 75, ASPH-G
BTP, 08, 3998, 100, ASPH-F

Pavement doesn't seem to be a requirement either.
PBV, 11, 5000, 150, GRAVEL-G
UBW, 05, 6000, 130, GRAVEL-G
KSM, 16, 6003, 150, GRAVEL-G
UNK, 14, 6004, 150, GRAVEL-G

--kyler