taller tires killing gear ratios

i have a quick question, i plan on running a 295/50/15 and i want to put 3.73's in the back. I use to have the rear end ratio equations but i lost them, anyway if i remember correctly doesnt a 27 inch tall tire (295/50/15 arent 27 tall but the bfg's im getting are) wouldnt it kill 3.73's to 3.55's? maybe id want something lower than 3.55 though, for my supercharger im gonna be putting on soon?

thanks,

Drew

mr yount you always come through, you deserve a medal or something for the most helpful person on stangnet, mos def.... yeah i know they are 26.6 inches but the bfg's im gonna get are listed as 27 and i called and they said they were actually 27 inches. and thanks again for helping me out

Drew