car won't turn over even with new starter

put car in neutral and see if it will roll freely. If no then I would check into trans issues. If it will roll freely then but wrench on harmonic balancer nut and try to manually turn engine over. Are you positive that car did not jump time or timing belt break? If it did you probably have bent valves. I have seen these engines lock up due to the valves and Pistons being drove into each other. Let's hope not tho.

Rolls freely in neutral, especially considering it weighs 4,000 lbs. It worked and ran fine until it was parked about 3 months ago.

Ok. I would check your acc belts.(alter-ac and power steering). I have seen these seaze to the pulleys not allowing them to turn. Loosen the belts from the pulleys (I take them off in this case) then try to start car. If car starts turn off ASAP. Then inspect all pulleys spin freely before replacing the belts. Any hung pulleys will need replaced.

If that don't work then I would remove the spark plugs and spray some WD40 in each hole. Let it sit over night. Next day put wrench on harmonic balancer nut and work it easily left and right till it spins freely.(have seen piston rings seize to cyl walls after being parked awhile) Now with plugs removed try starter to turn over engine. If it does turn over put plugs back in and start your car.