I was just wondering if I could run 42lb injectors on my stock 5.0 with an EMS8860 computer? would the pulse width be too wide or too much fuel delivered? Not much difference in price between reco stock and 42's

I'm not sure about the Pulse width of them, but if you're not planning on fairly heavily modifying the car, there's not really any need for 42lb injectors. Although i know where you're coming from on the price of them compared to the 19lb ones.
The EMS should be able to run them, AFAIK.