I believe that you would want to ask for the parts for a '84 Chevy K5 Blazer. As I understand it, all the CUCVs were made to the '84 standard no matter the year to help cut down on parts inventory. There are a few exceptions (like my locking hubs in my '84 are a little different and take a different tool than the '85 and latter ones) but by and large I think this is the case. Good news is these parts should all be readily available and cheap.
Good luck, brakes are the 2nd most important system on a truck in my option, right behind steering...
Christopher
Yes, you order parts for a 1984 K5 6.2L 4WD regardless of the year you have.
You are also correct that the hub socket is different from the 1984 and 1985+. This is why I have the socket set that covers both and the 14-bolt as well.
Axles, make sure they are the 10-bolt.
I just spent $200 on parts today to replace all the calipers & wheel cylinders. Also replace the harmonic balancer and change the axle fluid on both. These are repairs that I do to all the M1009 trucks I get before I complete them to resell. These brake parts are cheap, so spending that money is just simply worth it to have a good braking system. The balancer I change just because after 25 years who know if it was ever replaced.
(Edit) Make sure you check the balancer at the parts store for any damage, there is no packing in them and I one time had one with a dent that I rejected purchase.
O'Reilly Auto part numbers
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Cardone Friction Choice - Brake Caliper
Part # : 18-4208 (Right)
Part # : 18-4209 (Left)
BrakeBest® - Wheel Cylinder: Part # : WC51081
BrakeBest- Disc Brake Pads: Part # D52
Precision Parts Powerbond OEM - Harmonic Balancer: Part # : PB1102N
Fel-Pro - Differential Cover Gasket: Part # : RDS55028-1 (Rear)
Fel-Pro - Differential Cover Gasket: Part # : RDS55075 (Front)
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