Carpeting Issues- non molded carpeting

My car came with a brand new carpet sealed in a box in the trunk. Today I tore the carpet out and prepared to install the new carpet. Unfortunately, it's not molded. The front part looks like it will fit fine with some trimming, but the rear section will need to be molded to the floor pans to fit right. Should I just go at it with a heat gun? Is there a preferred technique, or is it a lost cause? I'd hate to drop the money on a new carpet when I've already got one.

My other option, is to keep the old rear sections and install the front. The rear is fairly clean, but is faded. The old front section is in terrible shape though, and only got worse when I tore it out- a previous owner had put 4 screws in to hold the carpeting down around the heel rest. Those were a joy to remove.

Thanks for the input!
Author: admin