I did use aluminum stick welding once, it was a bit trickey and looked like S***, but it did work. The rods I had were 1/8 for DC. I don't know the actual amps, but it was probably arround 100, the engine drive I used doesn't have specific settings. Remove ALL flux when done, if I remember, it becomes corosive when wet.
Pre-heat for sure, We used to heat with a carbourizing flame untill it was black ,Then heat with a nuetral flame until clean,a quick wire brush and weld . I can't remember the rods we we're useing. The welds turned out looking ok - not great. Would not be my first choice for repair unless I had no other means of welding.