I was assuming you had a tower, and wanted the best of the best. Since you are talking about a simple push-up pole, I will have to agree with Radioguy7268 that the DB404 would be overkill, and might tend to overload the support pole when iced. The DB404 would survive the ice, but might not survive the fall to the ground when the pole snapped.
My next best recommendation for you would be to look into a Comet CA-712EFC for about $150. Much lighter weight. With the money you save on the antenna, and since you are going about 120-150 feet for the coax run, I would take that saved money, and put it into an extremely low-loss coaxial cable such as LDF4-50A Heliax or similar. If you can save 3dB of loss in your coax cable, you will literally be doubling your power to the antenna.
If you do decide to go with the Comet for GMRS, be sure to order the model with the "C" on the end. The popular CA-712EF is a Ham antenna tuned for 430-450 MHz. The one ending in "EFC" is the commercial version, tuned for 460-470 MHz.