I always use RTV sealant when installing a timing chain cover. I have found that I have moderate success at installing the timing chain cover with a new seal and without dropping the oil pan by installing and tightening the bolts along the bottom of the timing cover first. Putting these bolts in fist tightens the timing chain cover down to the oil pan and compresses that thick new rubber seal. Eventually the rubber seal is compressed enough to permit the timing chain cover to pop onto the locating dowels. You should loosen the first few bolts on the oil pan when you do this, and you will also need a bit of RTV sealant in the corners of the rubber gasket.