they wont fit into the fuel rail or they plugs wont fit?
if they wont fit in the fuel rail grease up the orings and push HARD or LIGHTLY tap them in with a small hammer and punch(VERY LIGHTLY it shouldnt take much)
if the plugs arent fitting, check that the pins arent bent and put on some dylectic grease, make sure your plugging them in correctly since they only go in one way
no they should just hook up normally with no modifications at all.
I was able to install stock sr injectors with no problems but these
had a smaller plug so the stock ka plugs would not fit into the socket.