You could use -stim_times_AM1 and add a bunch of indicators to your married files, like this bash session:
$ cat times.1D
10
20
30
40
$ cat durations.1D
3.5
2.7
6.5
5.3
$ n=$(wc -l <times.1D)
$ for i in $(seq 1 $n); do
> yes 0 | sed "${i}s/0/1/;${n}q" >temp.dummy$i.1D
> done
$ paste -d, $(seq --format=temp.dummy%.0f.1D 1 $n) |
> paste -d\*: times.1D - durations.1D >married.1D
$ cat married.1D
10*1,0,0,0:3.5
20*0,1,0,0:2.7
30*0,0,1,0:6.5
40*0,0,0,1:5.3
Now you can use married.1D as a -stim_times_AM1 file to achieve the same effect as a duration-modulated -stim_times_IM file.
Be aware that this code as written isn't clever enough to handle a file with local times.