I have a 94 ford e150 with a 5.0 and the ecm tested bad a guy sold me a used 1 from a 5.8l and said it would work being stupid i bought it are they interchangeable?

 

Can we ask what was the problem that it was determined the ECM was at fault.
I cannot really say if the 2 ECMs are interchangable , but if there is a problem within the vehicle that destroyed the original ECM, it most likely could destroy a replacement ECM and should be checked before installing the replacement.