Starting issues

[NewScoutGuy]

I bought my first Scout a couple months sgo, 1979 Scout 345with manual trany. Motor recently rebuilt but was told needed starter when I bought it. I have had 3 different starters and all have just slowly turned over the motor. I had a mechanic rebuilt carb and spent 2 days trying different things. We replaced wiring, checked with meter13.9 at bat, 13.8 at coil, 13.7 at starter. Tried to adjust timing. When mechanic tried to turn motor by hand using breaker bar, with belts off he thought it was very hard. We pulled all plugs but no change.
Because Scout sat for over year after rebuild he thought May be issue in motor - mouse nest or something so suggesting pulling trany and if still no change pull motor and take a look. Motor is currently hanging in shop, pulled head and dropped pan but no obvious issue. I can turn with socket and 1/2 ratchet but takes nearly all my strength.
Any suggestions would be greatly appreciated

 

[FDChappie]

Only thing left is a spun bearing. You're almost there so pull it the rest of the way apart. I'd remove the cam first and see if that helps, then pistons. If it's still stiff you know know it's the main bearings.

 

[1975IH200]

1. Check to see if the flywheel attach bolts are the correct length, ie. Not too long and hitting the rear of the block.

2. Also, the starter uses a spacer with the tf727 auto trans, no spacer with a manual trans. Possible interference if this configuration is not correct on the engine.

I am curious about how you "tried to adjust timing" ?? Were you successful or not? What did you do? IH sv-8 engines are timed off of cylinder #8.