buy new transmission but don't understand gear ratios

[Bjj_junkie]

hey everyone, after doing as much research as i can and talking to the few people i know that know some about the subject. i concluded that ill buy the same transmission i have in the truck now just rebuilt from a site. i have a 72 step side with a 250 and 3 speed floor shifter. the transmission is no good as it is and it seems to cost more to get it rebuilt. I'm not sure if its a muncie or saginaw but ill find out once we pull it out. after looking online for some time i finally found a site that sells both muncie and saginaw rebuilt 3 speeds but theres 5 different gear ratio options and i have no idea which would be the one i need. If anyone could help me understand this a bit more and recommend which would be best for a daily driver that would be awesome.

they start at 254-150 and go up to 351-189

heres the site I'm talking about if you can make sure this is the transmission ill even need because i see the site is strictly racing so I'm not %100 sure this is even what ill need http://www.smileysracing.com/shopping/?ic=1574

thanks a bunch