reseting ring gear?

[john rod]

'67 C-10 Suburban, 12 bolt truck, 3.73 open.
after 273K on the clock, the rear is getting very noisy. i am hoping to move the ring gear towards the pinion to take out excess backlash.
my questions are: what does a spreader look like, can i make one, and how far can you spread the housing?
12 bolt shims are very hard to come by, at least in this small town. will anything else work?

thanks
rod in AZ

[john]

With 273K on the clock you probably need new bearings more than to reshim.