hi miles who knows $800-1000 ,verifiable under 75 k longblock $1,500. refreshed longblock, heads gone over, new rings/ bearings, timing set oil pump and so on $2800-$3000.00 and up for upgrades.
at very least if unknown do valve springs, gaskets/ seals, water pump, timing set, and related parts if you buy a used motor. 10x easier with it on a stand vs in the car.