Chevy rearends question

[80 Chevy K20 4x4]

I'm wanting to know if the 67-72 Chevy 4x4 front and rearends can be swapped out with 73-up front and rearends? Do they have the same spring pad width? Is there any difference in the lower shock mounts? I know the pinion yokes are different and would require an offset u-joint, but need more info. I'm trading my 89 K5 lifted Blazer for a 68 Chevy SWB 4x4 pickup and it has 5.13 gears front and rear with detroit lockers in each rearend. I want to go to 4.10's, but want to know what my options are.

Thanks for the help,
Doug

 

[Triaged]

The fronts have the same mounting points but the pre-73 stuff has small D30 sized u-joints (260x) unless he has swapped the shafts.

The rears have different spring pearch width (40in vs 42in or something like that...the older stuff is the same sepperation as a 73-up 1-ton) and the shock mounts are different as well.

 

[cornfed]

Is your rearend 3/4 ton or half ton? If its a factory 3/4 ton Ill buy it if you swap it out.