For those of you experienced WFRPG folks ... I have the bestiary and core rules for WFRPG, but I have the current 4e release of The Enemy Within. Do you think I can just run the campaign with the 2e rules?
There are some differences between 2E and 4E in regards to damage output and wounds.
Wounds. In 2E your starting wounds are between 8-14. In 4E you generally start with more. It's a calculation based on three different stats, but it's usually around +2-4 in 4E when compared to 2E.
Damage. In 2E a sword does 1d10+SB (strength bonus, the tens digit of your strength score). In 4E a sword does SB+4+SL (success levels, how much your attack tens dice beats your target's tens dice to defend themselves). This is effectively 1d10+SB+4...but you're generally going to get on the lower end of that 1d10. So damage is a bit more in 4E.
Comparing the starting Mutants from the Enemy Within 1E and 4E (there was no 2E Enemy Within, but it's close enough)... we get...nearly identical stats...except wounds are basically doubled.
Same move, weapon skill +15% in 4E, same strength bonus, same toughness bonus, intelligence is the same, dex is +1% in 4E, willpower is +5% in 4E, and fellowship is +20% in 4E.
So if you're running Enemy Within 4E using the 2E system, I'd halve the baddies' wounds and give them a -15% on combat skills as a baseline and adjust from there. But that's from literally just glancing at two stat blocks, so take that with a big grain of salt.