Junkyard 360 found...should I pass on a modded motor? pic..

Go to the yard and pull the dipstick and look at the oil. Open the radiator and look at the coolant. Pull the plugs and note what each cylinder plug looks like.

Have them start it up and let it warm up to operating temperature. Look for smoke, water vapor, etc. and listen for knocking etc.

Have them drive it around the yard to verify that it is in "good running order". Listen for knocking, pinging, noises with the motor under load.

Shut the motor down. Pull the dipstick and look at the oil. Open the radiator and look at the coolant. Pull a valve cover and look for sludge/old oil. Pull the plugs and note what each cylinder plug looks like.

Offer them what you think is fair.