Most important part is to straighten the flange on the cover. I use a 216 cover on my 235, I hate the 4 bolt design, you have to really glue the gasket with the 4 bolter. Felpro makes two thickness for this gasket, get the thicker one, if you can.
One 250 that I had needed a new cover, the old one was bent and kinked. I finally straightened the best I could and put it on with blue rtv, no gasket. It never leaked again, but was a sob to get off.
