My 91 chevy 1500 has a 79 350 block. After cranking it in the morning and riding it hard to start back up. Sound like the starter dragging.
Load test the battery. If that checks out, test the starter. It may be getting lazy. If that checks out, check your ignition timing. If it's too far advanced it can cause the starter to drag or crank slowly when hot. HTH. -Jim