I think the carlton automotive cosworth replica rear 1/4 panels go all the way up the rear quarter like a true cosworth, if you wanted to build a more realistic replica like RS Monkey is suggesting.

However, for the price you paid you cannot complain at all, get a nice engine under the hood like you are planning and it will be a nice motor you have there!

One thing i would do however, is not have it badged as a cosworth