Exact same setup as mine - except for the engine.
I recently installed new calipers and spent a lot of time looking for exact replacements for the factory installed calipers.
You probably currently have the Bendix Single Piston Sliding caliper style - like this:
You must be registered for see images attach
That is GM part number - 19242898/19242899.
A new set of these - when I looked - was about $400 ($200 per side give or take).
Here is the left side at Nalleys:
CALIPER. Wheel Brake Cylinder/Caliper.
1986 GMC K35/K3500 PICKUP 4WD. Stock Code 19242898 ; 172-2061; 1722061
Manufacturer GM
Categories Brakes > Calipers and Wheel Cylinders
Assemblies AXLE ASM/FRONT; BRAKE ASM/REAR DISC; BRAKE CALIPER-FRONT & REAR DISC; BRAKE CALIPER/FRONT; BRAKE CALIPER/FRONT & REAR DISC; BRAKE CALIPER/REAR; C310,314 BRAKE CALIPER/FRONT; C310,314 BRAKE CALIPER/REAR; G315,318,319 BRAKE CALIPER/FRONT; BRAKE CALIPER/FRONT; BRAKE CALIPER/FRONT; BRAKE CALIPER/REAR; C310,314 BRAKE CALIPER/FRONT; C310,314 BRAKE CALIPER/REAR; C BRAKE CALIPER/REAR; R BRAKE CALIPER/REAR; ; C310,314 SUSPENSION/FRONT; SUSPENSION/FRONT; DISC BRAKE ASM/FRONT;
List Price $ 296.66
Your Price $ 178.00
You Save $ 118.66 (40%)
The RH side is $219.
That's without pads.
http://parts.nalleygmc.com/showAsse...odel=14584&modelYear=1986&ukey_category=19426
Rock Auto has them for $143/177 - LH/RH
ACDELCO Part # 1722062 {#15665668, 19242899} OES
CALIPER,FRT BRK RIGHT HAND; w/HYD PWR DISC/DRUM BRK(JB8) or 4-WHL DISC BRK(JF9); INCLS BOOT,HSG,PSTN,SEAL,SHLD,VLV
ACDELCO Part # 1722061 {#15665667, 19242898} OES
CALIPER,FRT BRK LEFT HAND; w/HYD PWR DISC/DRUM BRK(JB8) or 4-WHL DISC BRK(JF9); INCLS BOOT,HSG,PSTN,SEAL,SHLD,VLV
CALIPER,RR BRK LEFT HAND; INCLS BOOT,HSG,PSTN,SEAL,SHLD,VLV
https://www.rockauto.com/catalog/raframecatalog.php?carcode=1163012&parttype=1704&ck[mkt_US]=true&ck[mkt_EU]=false&ck[mkt_CA]=false&ck[mkt_MX]=false&ck[year_1994]=true&ck[viewcurrency]=USD&ck[ID]=0&ck[idlist]=0&ck[PHP_SESSION_ID]=16o8ubseq60phpmtbaanf1j9e4
Those are new ACDLECO, unloaded - but because they're not remans - there is NO CORE CHARGE.
I bought a pair of ACDELCO remans (by Wagner) for about $100 combined. But that included $40 in core charges - which I ate.
They (the Wagner rebuilds) seem to be okay. I had some issues with getting the bleeders & hoses to seal. But once I got past that they have been holding.
NOTE: they have not seen much road time yet. I am restoring the truck and it spends most of it's time in the garage.