This is NGR (Not GS related), but I have a vehicle with drum brakes.   One drum brake pulses, but I thought only disc brakes pulsed?

Yes. A drum can get out of round. Or it can develop rust on one side if left sitting for a long time. You can have the drum machined if there is enough material left in it. That will cure the problem. Might as well replace the brake shoes while you're in there.

Thanks.

or if youre bored. err anyho can always convert to disc. i had build with a lady friend of mnine a 69 chevelle. me, her, adn her BF buit that engine. a 383 stroker./powerglide damn thing liked to go. BUT did not like to stop. had 4 drums lol. those were hell she bought. and i installed a disc conversion. now its fun to drive. will get up the pics of it one of thewse days. that engine is bad assness all the way around