question about my 72 burb

[WOLFMANmike]

i have a 72 burban 3/4 ton i was wondering in anyone knows what the most common gear ratio is in the burbs back then ? i know originally it is a small block burb and its a 14 bolt floating axle rear end .. dont know if this info help you help me or not ? but im looking for a way to know what it has now and what i can change it to to get better MPG out of it lol i know mpg thats funny with such a heavy beast but im sure i can pull some out of it somewhere

ty in advance for any help you offer me