Seized Motor

Looking for some opinions. 1984 3/4 ton Scottsdale 5.7L, 4 barrel carb, 4 speed manual, heavy duty cam installed when it was only a couple years old. No catalytic converter (3/4 ton didn't have them that year), around 187,000 miles. Truck did a lot of hauling and towing including a 29 ft camper. Had some electrical issues (fuse link replaced next to the firewall) and brake issues. My dad bought it new in 1983, always smoked a little taken to the dealer several times while under warranty and they could adjust to either white or blue smoke but never completely got rid of it. Only used about 1/2 quart of oil between 3,000 mile oil changes. Truck was my daily driver from 1990 till 2000 then switched off between it and my 1990 Silverado 3500 7.4L. I helped take care of this truck from the day my dad brought it home, I learned to drive in it, and it was my graduation present in 1990. As many on here can probably relate it is still my baby. History lesson over - didn't have time to deal with the electrical and brake issues so the truck sat for about a year and a half. Finally decided it was time to put it back on the road, everything was back in working order but it was running real rich. Several weekends I ran it around the farm figuring with the fresh gas it would clear up then one weekend while it was just idling outside the garage for about 10 minutes it just stopped. Oil level was full and oil pressure was running normal before it quit. When it stopped I was standing within 20 feet of the truck and didn't hear any noises it just sounded like you shut the key off. Now you can't turn the motor by hand and it very slowly turns over with the starter and doesn't attempt to fire (the plugs are sparking).

Now for the opinions - should I have the motor pulled and opened up to see what happened and if feasible to fix it or just go straight for a new motor? Haven't done any research yet so I have no idea how expensive either option would be. Any opinions/suggestions would be appreciated.