He can't just use another cap if its an avs motor because an avs motor isn't threaded in the pan like a non avs is. I tapped the pan in mine, but honestly I don't remember the actual size pipe tap we used. I believe it was 3/4 npt but I can't swear to it. Then I just put a pipe plug in it. I made a dipstick from all thread and put a knob on top of it. Change the oil and filter, put in the amount of oil that you run, then pull the plug out, slide the dipstick in and where the oil level is on the dipstick is where you mark it. Then you can pull the plug and check your oil with the dipstick. Works great and is a lot neater under your hood.