I have the same tank in my Dart, NHRA tech required me to have a rear firewall because of it.
Just something to think about.
I still have a back seat and no roll bar. (yet)
Only thing I can guess as to why you would need a rear firewall would be because it's not an OE part. Other than that, kind of makes no sense but what do I know. Guess we will see when I get to the track this summer.
