With the help of many of you I've finished my upgrade of a MS310 from a 46 MM jug and piston to that of an old 039 I found. It has turned out awesome and I am very excited to get it in to some wood.
Success, a friend had a twin base 60 inch white oak that was ready to start dropping dead branches where his children play so I got to exercise the MS310/039 conversion. With a 28 inch bar full chisel stihl chain and about 90 min the tree was down. Not an arborist by any stretch of the imagination but was really impressed with the torque this put out. Didn't have any issues with bog or sticking. Thanks goes to the professionals and hobbiests here on the Arborsite!