[David R Leifheit]

Keep in mind that the auto parts stores, and many shops, use data bases which call for Chevrolet parts as if there was no difference between trucks. Which means there are often times when the parts you need are "wrong" in their opinion.

It is easier, in my opinion, to take in the old part or the numbers off an old part so they can order the correct replacement.

My '63 had a LOT of those issues, since it is a 2500 (1-ton GMC, 3/4 ton Chev).
Had to replace the master cylinder, they argue it doesn't have hydraulic clutch (GMC did, Chev didn't) so got the wrong part the first time. Rear wheel cylinders are the same on a Chev, right and left on the GMC (computer only shows GMC and Chev as the same). And don't even get into the 1-ton v. 3/4 ton differences...

Whatever your truck has for brake shoes now, if they work and fit, are likely the correct ones for your truck. Regardless of what a shop or parts house tells you.

According to the manual X-6523
Front Brakes on a 1500 are 11 x 2-3/4
Rear Brakes on a 1500 are 12 x 2-1/2

So it looks like you have stock brakes...