Denny, there might be an easy way to check. Do it outside so that you don't paint the walls of your garage with oil.
The circuit is reversed for the oil filtration when you push in the dowel. What I mean by this is that the flow for a bypass filter (dowel out) goes from the oil pressure gauge fitting (feed side) to the filter to the fitting in the block that drains to the sump under the dowel (return side). When you push in the dowel for full flow, the flow goes the other way. The feed side is from the fitting under the dowel to the filter (or not) to the return at the oil pressure gauge fitting.
Be prepared to shoot some oil everywhere, but you should be able to spin your oil pump with a drill with both of your existing lines disconnected. If you get a geyser from the oil pressure gauge fitting, the dowel is out and you are set for bypass. If you get the geyser from the fitting under the dowel, the dowel is in and you are set for full flow.
I mention 'or not' above because you don't need to have a filter with the dowel in the full flow position, but if you don't have one, you still need to have a 1/2" line connecting the two ends of the flow circuit or you will starve the engine of oil.
The shadetree approach given above might not be bullet proof, but I'd sure trust it more than just guessing!
Remember, if you try this test, you'll shoot oil everywhere out of the open fitting(s). I know from spinning one up and accidentally not having connected one of the lines!
Matt
