A 1956 should be casting No. 3836340 and what I read out of it, it doesn't have the dowels. I think your question fits very much into the discussion because you have a 261 and we are discussing serious business, but I'm not a moderator. If yours had a bypass filter or no filter you should be ok. But on any engine rebuild, and probably more so a 261, its a good idea to check for oil circulation before firing them up. Lots of people stick a screw driver blade in the oil pump and turn it. I don't like that because I have seen people reinstall the distributor and not get the distributor in the slot and still starve the thing for oil. I like to pull all the plugs and crank the engine for about 10 second intervals and watch for oil at the rockers. I keep a battery charger on the low position during this cranking. Starters can stand a little too much voltage better than too little.
