I have the same housing as the '84 we had them on the diesel trucks til 90 something... I have 1,5" spacers bouth front and rear and have been driving with them for over a year now with out any problems. (except for broken pinion bearing after a long and hard jump) I donīt thing the spacers have addet more stress to the bearing if I wouldnīt have the spacers I would had to change my rims. The only diff. is that I have the bigger drum brakes but it dosnīt seem to make more difference either not when you have that big wheels 39,5".
I am waiting for my order from frontrange offroad to arrive so I can install my full floating and disk brakes 
I desited to go that way after brakeing a rear axle doing 50 m/pr h  and loosing the tier not a plesant experience.
The axles doesnīt seem to bee any stronger in the longer housing at least by the look of them. and the housing looks the same streanght. I have actually seen more bent housing from the new housings than the old.