newer ones will not fit, the 86-88 valves have been discontinued. I was looking for a set for a 88 cylinder I was working on, only to find that I couldn't get them. don't know if they are the same as 250, I'd doubt it. I contemplated machining a aluminum shaft and driving it into the valve hole, then cleaning out the port, I knew I'd lose bottom end, but I had other mods that enhanced the motor so I wasn't concerned. I thne found a cylinder on ebay and it had good valves, I'd say that woulod be your best shot.