My 1989 turns over but won't start - 1990 Chevrolet K2500

What have you checked so far ?
Is the coil getting power and a ground signal ?

remove the distributor cap and dry it out with a blow dryer and put it back on.

Check the battery cables for tight and clean connections. Also make sure the are not breaking or frayed especially by the starter.

may need a crank sesor

check fuel pump relay, fuse, if ok , fuel pump needs replaced

ck fuel pressure at pressure test port first.

Check starter, spark and fuel pressure.

sounds as the barrel is broken or malfunctioning. you will need to remove the plastic cowling to gain full access to the ignition barrel which may give you a clearer picture of whats actually wrong. sometimes the steering lock tab gets jammed preventing full key turn

hard starting on hot engines is caused by just 2 things:

1. carbons in starter needs to be replaced.
2. ignition timing is overly advanced. timing should be recalibrated by your mechanic.

do you have an overdrive trans, the overdrive solenoid might be sticking locking the trans in overdrive
causing the no start