[TheAvengers2]

new String:g_sOldModel[64][128], g_iOldModelPos;
new String:g_sBodyModel[64][128], g_iBodyModelPos;
new String:g_sHeadModel[64][128], g_iHeadModelPos;

public OnPluginStart()

    new Handle:hndl = OpenFile("models.txt", "r");
    decl String:sBuffer[128], String:sBufferArray[2][128];

    while (ReadFileLine(hndl, sBuffer, sizeof(sBuffer)))
    {
        if (ExplodeString(sBuffer, ";", sBufferArray, sizeof(sBufferArray), sizeof(sBufferArray[]))
        {
            if (StrEqual(sBufferArray[1], "oldmodel"))
            {
                strcopy(g_sOldModel[(g_iOldModelPos++)], sizeof(g_sOldModel[]), sBufferArray[0]);
            }
            else if (StrEqual(sBufferArray[1], "hs"))
            {
                strcopy(g_sBodyModel[(g_iBodyModelPos++)], sizeof(g_sBodyModel[]), sBufferArray[0]);
            }
            else if (StrEqual(sBufferArray[1], "oldmodel"))
            {
                strcopy(g_sHeadModel[(g_iHeadModelPos++)], sizeof(g_sHeadModel[]), sBufferArray[0]);
            }
        }
    }

    if (g_iOldModelPos != g_iBodyModelPos || g_iBodyModelPos != g_iHeadModelPos) // a problem?

    CloseHandle(hndl);
}

for (new i = 1; i <= g_iOldModelPos; i++)
{
    if (StrEqual(oldmodel, g_sOldModel[i], false))
    {
        strcopy(bodymodel, sizeof(bodymodel), g_sBodyModel[i]);
        strcopy(headmodel, sizeof(headmodel), g_sHeadModel[i]);
        // do something?
    }
}

I think this is right... I haven't tested, nor am I familiar with the functions.