Print file 83.obj from part 8 as big as you can, than print the rest of the files at the same magnification... boom big skull on your wall!
5 min epoxy, c clamps, a small model to look at, gloves, mask, plastic wood fill, texture paint and a lot of time.
I have a 200x200x180mm print bed. I printed at 6.66x with10% infill, supported, and in PLA = 1 meter long skull.
Use a little time to figure out the least wasteful, least time consuming way to print large prints. Spend some time with 83.obj, it took me a while in cura to figure out the best way to print at 6.66 scaling.