Roof Oddity

Okay I'll be the first to admit that i'm kinda un-initiated when it comes to certain things in restoration.

for example, on my 'new' 74 Valiant Brougham the roof has what can only be described as a 'luxury option' the roof is not actually metal on top, it is this odd feeling material that crumbles at the touch. I'm assuming that when the material was factory it must have felt something like a 'spray on bedrug' that some one would get in the bed of their pickup. I've seen simmlar things on the roofs of cadillacs from the mid 90's. but now i've got it on the top of my Valiant and I need to know how to do one of two things

1. scrape it off and put a real metal roof on
or
2. make it not so crumbly and restore it to something like a factory feel.

I'm sorry if this seems like a stupid question, but i'd appreciate help.