3 bolt rear. Run like the wind if you ever see one of these
4 bolt is the only real choice for a decent 1G. The thermostat thing isn't a safe way to check a block since it can have any combination of head etc. Trust me, I found that out through experience. Just when you think you know what you bought, you get home and realize there is no front motor mount point because it is a 2G engine in your 1G. So to find out if it is a 6bolt or 7 bolt, look at the front of the timing cover where it meets the oil pan, if the oil pan remains flat at the flange all the way around that area, it is a 6 bolt. If it has a dip down it is a 7 bolt and if it has provisions for a front engine mount on the block it is a 1G seven bolt, otherwise it is 2G engine.
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