My conversion but more likely an A&M engine.. Walker engines had a white delrin ring on the front for the sensor..
Look at the con rod, if it's copper colored the crank is a Sachs..Walker 4.2s have the top 2 crankcase bolts parallel to the bottom 2, A&Ms were not...The cases are otherwise identical, and if the crank is a Sachs the engines will run the same..A&M cranks were not known for their longevity....