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The roller looks way too narrow to me. Roller rockers sold by speed shops have a similar sized roller over the other end meant to reduce side loading on the valve stem. Rollers on the cam typically are similar in width to a "plain" cam follower. Don't mean to sound critical, but these are highly loaded components.
Also, If you mean to use standard cams, the roller will need to have the same radius as the standard pad or the effective cam profile will be radically altered.
regards,
Phil
What Phil said is the most important part! The radius of the original rocker is pretty big, a roller with the same radius would be so big that there is probably not enough space under the valve cover to accomodate it.
Plus, the weight of this gigantic roller, which should indeed also have the same width as the original follower, would be as great or more as the complete old rocker, so the total weight of this new rocker would be double of the original one.
The only way to do this, would be to use the smaller roller together with a specially engineered cam profile, but then it is beginning to get expensive, not simply swapping rockers!
Sebastian