Congrats on your purchase of a '79 444 Marlin, mine is a '76 Marlin 444s, I too am glad not to have a CBS to be an irritation. I use IMR 4198 in my .444 pushing 265gr Hornady's, that should work for you too. You can start at about 42gr & increase from there, mine are cooking on 44.5gr IMR 4198 & a Federal Magnum primer.
--Ken <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />