The use of a file sounds hokey to me. If you have access to a lathe, you can get professional results. Also, the tang engagement in the oil pump should be thought out using measurements from a 235 distributor. Also, pay attention to the cam (is it cast or steel billet?) as this will make a difference on whether you use a cast or steel distributor gear. If you aren't sure what your cam is, order a bronze gear from summit or jegs.
Some folks cut the shaft off and bore out the end leaving a 0.030 wall thickness or so. Then turn down the end of the original 235 distributor shaft to press fit into the bored HEI shaft at the gear location. Then drill through the assembled shafts at the gear pin location and assemble as a unit using locktite bearing mount adhesive.
