92 1ton single axle vs 1ton dually. both conventional trucks not cab and chassis. whats the difference between the two diffs? is it hubs and studs or??

The dually will have longer studs to accommodate dual wheels and most likely use drums for coined rims and flat lug nuts.
And of course the hub extensions for the front.

Assuming this is Cummins, same as above, maybe a different width rear end...

its cummins. its for a customer who wants to go dually. I assumed diff was the same just the hubs and studs were different.

found the info.
srw 53"
cab/chassis 55" 5/8" studs
Dually 60" 5/8" studs

'72-93

SRW 65" WMS
Dually pickup 72"~ WMS

Front axle differences are the wheel hubs. There are not spacers on the older trucks like the 94 and up. 94 up front axles have almost nothing that swaps with the older style, nor is the newer axle swappable as a assembly. The good news is that lots of folks will trade srw hubs for drw hubs, me included...

There are 3 different rear axle widths for 93 and earlier trucks, iirc the widths were posted above. If you are running a flatbed the width isn't that critical but for a pickup bed you do need the widest axle so the inside wheel clears the bed.

I've heard but not confirmed that 94up srw axles are close to the right width for pickups.
Nothing wrong with the 5/8 studs on the dually axles