Pretty amazing work, but as an ex aircraft composites guy I'm cringing at his use of glass and wet layup method. A couple of observations:
There is no control of the resin/cloth ratio; excess resin, which he certainly has, greatly reduces strength. The resin needs to be weighted vs cloth and he definitely should be using a vacuum bag and bleed cloth to compact the layup and suck out excess resin. For strength it would be better to use S-glass or carbon fiber and nomex with an epoxy resin; it looks like he's using polyester boat resin, which has no strength. If he plans to bolt the engine sub-frame to the rear bulkhead I see enormous problems. A far superior method would be vacuum bag pre-preg or wet layup and an oven; for a car you could probably get away with not using an autoclave. I also notice that he has not reinforced his molds and there is a lot of flexing going on. It appears he is laying all the cloth parallel; 0°, -45°, 90°, +45° type of orientation will reduce warpage potential, and some sort of directional cloth can be used for load paths. His use of honeycomb is good, but depth with a tapered edge equals strength
There's much more, with lots of tricks like pulling plastic faced plaster male/female molds and removing only high spots, which saves an enormous amount of sanding time, etc. Unfortunately I have huge doubts this will be strong enough, especially with the center section design.
Cool project, I hope it works