problem installing cars

[hotrodmerc84]

ok i am having a problem installing cars,, i have 2 that work the 86 grand marquis and the lincoln town car,, but i tryed changing the taxi and the cop car with the crown vic, but then the game wont load would this effect any thing, some of the names in the downloaded car file have upper case letters, and the 2 cars i got to work are all in lower case,

for example

the grand marquis file looks like this(all lower case) Works

sentinel.col

sentinel.dff

sentinel.txd

then the crown vic taxi file is like this(some upper case letters)Dosent work

Taxi.col

taxi.DFF

taxi.txd