Swapping coils for leaves:

[conoverbandit]

Hey Y'all,
I got a friend who has a 69 lwb c-10 pick up with the trailing arm rear suspension set-up.The coils have long ago lost thier ability to hold up a load and he wants to see if there is any way to put leaf spring suspension in under his rig.He does have a 75 lwb 2 by parts truck with axle and leaves inunder it. Would this interchange? He wanted to set his 69 body up on the 75 chassis, but the frames are bent different, the 69 bends after cab while the 75 bends under the cab, so we figured that route was shot. So he suggested taking the rear suspension out of the 75 and installing inunder the 69. I told him I thought it would or could work, but just had a brain storm..... the 73-up trucks are narrower? then the 67-72's? I had a 91 k-5 that we sold and I took the hitch off the back before we sold it, tried to put it on my 75 k-10 and it was 2in to wide to fit, but it fit on my dad's 71 GMC 2 by truck no problem.If this is the case he'll either have to re do the spring mounting plates or find another rear. Lucky for him I got an eaton 8 lug (which is what he wanted to go with anyways) from a 71 chevy camper special, this axle should be the samw width (plate to plate wise) as his current one? am I even close here? Thanks for the help in advance,