Sounds great, mate. I have been working on something similar although with more pulpy Robert E Howard/Brendan Fraser Mummy style fear rules. The other main rules additions are autofire weapons for things like Tommy Guns and a Hard to Kill rule for Eldritch Horrors. Basically roll damage as normal– if the result is 6+ you do 2 points of damage, otherwise you do 1. It works surprisingly well, particularly if you don’t tell the players about it.