[JJR]

Hollanders shows two spindles used on an 88 c1500 2wd. One for a 1" rotor and one for a 1 1/4" rotor. The spindle for the 1" rotor came on 88-91 c1500 and had a 1 1/4" inner bearing surface diameter. The spindle for the 1 1/4" rotor(which is probably what you have) came on the following:
CHEVROLET PICKUP TRUCK 88 2500 Series; 4x2
CHEVROLET PICKUP TRUCK 88-91 1500 Series; 4x2, 1-1/4" thick rotor
CHEVROLET PICKUP TRUCK 89-91 2500 Series; VIN models "C/K", 4x2, 6 bolt wheel
CHEVROLET PICKUP TRUCK 92-98 1500 Series; 4x2
CHEVROLET PICKUP TRUCK 92-98 2500 Series; 4x2, 6 bolt wheel
CHEVROLET PICKUP TRUCK 99 1500 Series; exc. Silverado; 4x2
CHEVROLET VAN 96-99 1500 Series
CHEVROLET VAN 96-99 2500 Series; 7300 lb. GVW
GMC PICKUP TRUCK 88 2500 Series; VIN models "C/K", 4x2
GMC PICKUP TRUCK 88-91 1500 Series; 4x2, 1-1/4" thick rotor
GMC PICKUP TRUCK 89-91 2500 Series; VIN models "C/K", 4x2, 6 bolt wheel
GMC PICKUP TRUCK 92-98 1500 Series; 4x2
GMC PICKUP TRUCK 92-98 2500 Series; 4x2, 6 bolt wheel
GMC PICKUP TRUCK 99 1500 Series; old style (flat, pull-up outside door handle), 4x2
GMC VAN 96-99 1500 Series
GMC VAN 96-99 2500 Series; 7300 lb. GVW
SUBURBAN 92 1500 Series; 4x2
SUBURBAN 93-96 1500 Series; 4x2, vacuum brake booster
SUBURBAN 97-99 1500 Series; 4x2, gas
TAHOE/YUKON 95-99 4x2

'95 up have ABS sensors on the brake shield.
1-3/8" inner bearing surface dia.
Inner bearing consists of #LM48548 cone & #LM48510 cup.
Heavy duty chassis option code is F44..

15981299 R.
15981298 L.


For lower control arm: the 67-70 3/4 lower arm can come from the following:
CHEVROLET FORWARD CONTROL 68-70 20 Series
CHEVROLET FORWARD CONTROL 68-70 30 Series; 7200 lb. rear axle
CHEVROLET PICKUP TRUCK 67-70 20 Series
CHEVROLET PICKUP TRUCK 67-70 30 Series; 7200 lb. rear axle
CHEVROLET VAN 71 30 Series; drum brake
GMC FORWARD CONTROL 68-70 2500 Series
GMC FORWARD CONTROL 68-70 3500 Series; 7200 lb. rear axle
GMC PICKUP TRUCK 67-70 2500 Series
GMC PICKUP TRUCK 67-70 3500 Series; 7200 lb. rear axle
GMC VAN 71 3500 Series; drum brake
SUBURBAN 67-70 20 Series
SUBURBAN 67-70 2500 Series


If the 71-up 3/4 ton lower control arm can work they can come from the following:
CHEVROLET FORWARD CONTROL 71-72 30 Series; 7200 lb. rear axle
CHEVROLET FORWARD CONTROL 71-89 20 Series
CHEVROLET FORWARD CONTROL 73-78 30 Series; non-removable carrier
CHEVROLET FORWARD CONTROL 79-84 30 Series; drum rear brakes, sgl. rear wheels
CHEVROLET FORWARD CONTROL 85-92 30 Series; exc. hvy. duty front susp.; drum rear brakes, sgl. rear wheels
CHEVROLET FORWARD CONTROL 93 30 Series; exc. hvy. duty front susp.; drum rear brakes, sgl. rear wheels, w/o 9L6 brakes
CHEVROLET PICKUP TRUCK 71-72 30 Series; 7200 lb. rear axle
CHEVROLET PICKUP TRUCK 71-88 20 Series
CHEVROLET PICKUP TRUCK 73-80 30 Series
CHEVROLET PICKUP TRUCK 81-88 30 Series; std. duty susp.
CHEVROLET PICKUP TRUCK 89-91 2500 Series; VIN models "R/V"
CHEVROLET PICKUP TRUCK 89-91 3500 Series; VIN models "R/V", std. duty susp.
CHEVROLET VAN 72-78 30 Series
GMC FORWARD CONTROL 71-72 3500 Series; 7200 lb. rear axle
GMC FORWARD CONTROL 71-89 2500 Series
GMC FORWARD CONTROL 73-78 3500 Series; non-removable carrier
GMC FORWARD CONTROL 79-84 3500 Series; drum rear brakes, sgl. rear wheels
GMC FORWARD CONTROL 85-92 3500 Series; exc. hvy. duty front susp.; drum rear brakes, sgl. rear wheels
GMC FORWARD CONTROL 93 3500 Series; exc. hvy. duty front susp.; drum rear brakes, sgl. rear wheels, w/o 9L6 brakes
GMC PICKUP TRUCK 71-72 3500 Series; 7200 lb. rear axle
GMC PICKUP TRUCK 71-87 2500 Series
GMC PICKUP TRUCK 73-80 3500 Series
GMC PICKUP TRUCK 81-87 3500 Series; std. duty susp.
GMC PICKUP TRUCK 88-91 3500 Series; VIN models "R/V", std. duty susp.
GMC VAN 72-78 3500 Series
SUBURBAN 71-88 20 Series
SUBURBAN 71-91 2500 Series

This statement makes for some confusion: This arm (71-up) may have two different ball joints one being light duty, the other being heavy duty. I am assumming they would be different diameters.

I hope this info helps.