what do you mean by " My engine is sitting too low in the back "

What exactly do you think is not at the right height/angle , the engine or the trans ? If you have the stock trans crossmember, with a stock mount, and a stock tailhousing on the trans then the trans is where it s supposed to be, the engine mounts being not in the factory location will cause either the tailhousing to angle down if the engine mounts set the engine higher or the tailhousing will angle upward if the engine is lower. If the mounts move the engine to one side of the other the tailhousing will angle in the opposite direction from where the engine is shifted. There isn't a lot of room between the centerlink and the oilpan , assuming you have a factory pan so that might be a good guage as to the engine being high or low , a piece of 3/4 think pine ( 1"x?) is what I usually stuff between the center link and the pan if I have to hang the engine without a trans on it for a short amount of time.