If you have one of those load levelers to change the angle of the engine & trans bolted together and a helper, I believe it is easier to put the engine and trans in as a unit. However, the last time I tried that working alone, I could not get the U joint to slide onto the splined end of the driveshaft. I tried every little trick I could think of to make it go and nothing worked. I finally pulled the assembly back out, unbolted the trans from the engine and put the trans back in separate. Then I made four guide pins (long hex head bolts with heads cut off) and threaded those into the bell housing. Put a jack under the trans to get it on a slight angle, lowered the engine down and guided those aligning pins into the trans bolt holes. Once the input shaft splines aligned with the clutch splines, everything went right together. I have used those aligning pins several times since then, so it was worth the time spent making them.