Check "Tech Tips" for more information on the 235/261 oil system and by-pass modification (if needed) If your block has 1/2 inch pipe fittings coming out of the pump and leading into the oil gallery...you have a 261. All that is needed is to check to see that the passage from the base of the block up to the oil gallery is plugged. This is necessary if you want to divert all the oil from the pump to the exterior filters. There are several ways to deal with the exterior filter. My favorite is the bolt on mount that takes two conventional filter so it can be mounted anywhere you want and connected with good quality oil resistant hose. One caution....when you install the fitting in the rear of the block into the oil gallery, I would suggest using a 90 degree fitting so you can hug the block with the oil line to avoid any headers you might chose to install.
