The guides should be avilable at a good machine shop. The 3 3/4 sleeves   are  made for the 144. That will be about 165 cid. Have fun with your oliver. I'm pulling my S55 in local antique pulls. Will put the 3 3/4 sets in mine this winter. Than want to get a manifold set and carb off of a late 550. Maybe 45 hp, I hope. <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt=":D" title="Very Happy" /><!-- s:D -->  <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt=":D" title="Very Happy" /><!-- s:D -->