I have a set of Crower steel roller rockers on my 250 with the 1.75 ratio. The main thing about using aftermarket roller rockers is that a lot of them use a larger diameter rocker stud than the stock rockers do. The Crower rockers can be ordered with either size rocker stud, which does make life simpler. However, most roller rockers are also taller than stock rockers due to the locking adjusters supplied with the rockers, so you may need either a different valve cover or a spacer to get clearance for the roller rockers under the valve cover. I didn't need guide plates on the 250, and the lift with my cam is 0.499".
