Forge World tanks an Armoured Company can take are:
LR Vanquisher: HQ, Elites
LR Exterminator: HQ, Elites
LR Conqueror: HQ, Elites, Heavy Support
Destroyer Tank Hunter: Elites, Heavy Support
Slamander Scout Vehicle: Fast Attack
Griffon: Heavy Suport
(NB using the standard army list only, up-to-date version from GW site)