Most of the time you can just replace S with LS, though the only times you get issues are things that do odd things, like having RC networks to do delays, or oscillators. If you do all at one there is no problem with fan outs or fan in, as the families all have the same fan out and fan in irrespective of family, provided you stay in the family. ACT will also work, just you might need to buy a good number of DIL to SMT adaptor boards, a few dozen leaded components to use as lead donors, and a few hours of soldering to get them all done.