Look at where the oil filter goes. You will see a large pipe fitting above the filter. Now to the left of that.....if you see another large fitting (that was for an oil cooler on 4 bolt blocks) then you have a 4 bolt main block.
BUT....just because you do not have this second fitting to the left does not mean you do not have a 4 bolt block.
Sorry if that sounds as confusing as it was to type.