Changing to a 3 line pump is cleanest and easiest. By pass you'll have to cut the outlet line and buy a bypass regulator, or use a wix 30041 fuel filter if you can find one it will have a small bypass fitting with a restrictor in it. Or you can plumb in a tee straight leg from pump through to carbureator,dog leg of the tee will go to return line,you will have to make your own restrictor. I am using a fuel cut off valve for a lawn mower as my restrictor more open = more bypass,more closed=more pressure. At the shop I used to work at we just used a piece of brass and drilled a hole for a bypass,but don't remember the size. If you have a selection of carbureator jets at your disposal you could experiment with different size jets as a restrictor.