The issue with changing the axles to big pattern part time hub locking is the rear end has to be changed too............. Now..........
In the 70's, they made part time too, small pattern.........
I have put the kits in, changed the hubs, etc, it's really not that big of a deal if you are an axle type of guy. The stub axle, and spindle out is all you need, the inner axle and tube is the same.
It's just a matter of finding parts.
Don't expect as big of a difference in MPG as you hear, or the front driveline/knuckle joints lasting longer. Sitting in one spot is worse on them than running all the time, if grease is used.