How hard could it be to sell a 318?

Yes, that 904 will be perfect behind the 360. Just remember that the 360 will need some sort of balance for the converter. Weights, flexplate or..... since the 360 is internally balanced and the 318 is internal. I do think not shipping may be holding up your 318 sale. Someone might pay the shipping price if you would be willing to help from your end with some arrangements.

Good Luck!