That looks like the front engine mount. If so, the one that you have the nut off of and the other one toward the center don't need to be removed to pull the engine. Remove the two outer nuts and the engine should come out. The two inner bolts are carriage bolts and the square under the head may have rounded or the square hole in the front engine plate has worn allowing the bolt to turn. BTW, you need to remove the cotter pins before attempting to unscrew the nuts. Attached is a picture of what you're dealing with from the Service Manual.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
