I have never installed a stockinteriors carpet set, but not to long ago installed a Moss carpet set in Tony Barnhills red 64 Midget. Also, I have a hard time explaining how to do things. My suggestions are to start with the carpet that goes over the rear axle. Center it and trim any excess carpet off. I use a piece of chalk to mark and then cut 1/2 the distance from the edge to the chalk mark and then check it and if needed, cut 1/2 off between the chalk mark and the edge. Sooner or later, you will be almost up to the chalk mark or at the chalk mark. When it fits perfect, glue it down. I use contact cement and coat the carpet only and let it dry, then come back and coat the carpet again and the metal. Wait till almost dry and stick it down. Next I do the frame rails and then the area over the wheel wells. All glued. Next do the floor starting with the frame rails which I use glue on and then the floor carpets which I use double faced carpet tape. Last do the tranny tunnel, which I also use carpet tape. I like the tape because its easy to remove the carpets if needed and easy to replace the tape. I find it easier to actually do this stuff than try to explain to someone on how to do it.
Rik