Without seeing it, I would first glue a peice of plastic behind it to brace it. Press the crack together gently, plastic melts with the glue, so after it dries real good, sand it down and see if you need a bit of bondo to seal it up.
Before I built my Caprice hopper my mom stepped on it breaking the back quarter window posts so I took a soldering iron witout the tip on, melted the post together from the back and used bondo to smooth out it all out front and back and now it looks like nothing happened, you wouldn't know if I didn't tell you, and It's as strong ans before the accident because of it all being the same plastice and all one piece.
G'day all, im from south australia, ive been a lurking this forum for a few years.
and like what i see here lots of talent and awesome builds.
some of you may have seen my builds else where, i figured you guys would like some of my builds.
here some pics let me know what you think
heres my builds hope u all like them since i never post any pics well here u go
heres my caddy ( haters nitemare )
my monte cholo
my lincoln ( brown roots )
my 62 (el pulpo )...