I have added the function 'SPMG1' to 3dDeconvolve's -stim_times repertoire -- this just give the SPM2 difference of gamma variates, with no derivatives. So now you can do 'SPMG1' , 'SPMG2', or 'SPMG3'.
For 'now' in the previous sentence, read 'after the binary build that will take place tonight'.
The 3dDeconvolve -help output has also been adjusted to reflect these recent changes, of course. As a reminder, the -help output of the various programs is almost always kept current, while other documentation and Web pages tend to lag.