I did one years ago. The parts I bought were of a hammer fired design, it worked for a while, then the hammer broke. I did a reweld with a jig, before they started torch cutting the receivers.
Friend of mine did a 100% new receiver, it's nice. He designed a striker fired setup, which was much better than the hammer setup I used.
I have 2 torch cut Mark 1 kits, plus a large chuck of 4140 and some day I will build a Mark 1 off a new receiver. With .303 pretty much non existent now, there is no hurry to start this project.
Jason