At present, there is no option or combination of options to do what you ask (output model F statistics but not model coefficients). However, since I'm in the middle of making changes to 3dDeconvolve.c, I suppose this could be added. What most people do at the present time is to use 3dbucket to create a slimmed-down dataset from the fattened-up one created by 3dDeconvolve.
bob cox