I bought a Super Dexta with the engine frozen. Long story short, pulled the head, lots of penetrating oil and wacking with attempts to turn flywheel teeth with a bar, FREE'D it up only to find the injector pump was not giving fuel.
Oh sure, I honed the rust out of the liners...before I put the head back on.
Pulled the side cover to find it rusted froze. Again penetrating oil, latched onto rack with vice grips and wacked Vgrips and free that up.
Bled fuel, till clean fuel pumping at lines. Tighten them up and she ran like a dream.
Investment: $44 headgasket, lots of diesel, can of penetrating fuel and a lot of well placed time.
nearly 10 years ago, and that tractor still runs great, and gets used a lot on my farm.
Check the rack to see if it moves.