1/2 ton to dual axel rear?

[Back in Black 66]

i got a 74 chevy long bed half ton. my dad offered me to take the dual axel rear end out of his 75 gmc motorhome. its about a 20ft motorhome. it has the air bag suspension for weight adjustment. i always wanted a dual axel rear. and here is my chance. so my question is. what problems will i run into. i know the drice shaft will have to be changes out. but do i use the conplete leaf springs from the motorhome or keep mine. and will everything line up for bolting it in? and how do the fender extentions adapt to the bed, is it fiberglassed or bolted? i would like to use the same bed, it is in perfect shape, with no rust. thanks for your time in advance.