I also pay close attention to the drive nose (Protrusion) on the front of the converter and the inset of the crank where it fits.
Light smoothing out with a little sandpaper and a dab of grease.
Same applies for the dowel pins. Burrs on those will drive you nuts.
Make sure the converter drain, if you have one, lines up with the window in the flywheel. (Been there, done that. Had to pull mine out and re-clock it to match up)
Once you get it up in there and a few mounting bolts snug you should be able to grab one of the converter studs and rock the converter back and forth freely.
You should end up with a small gap between the stud mounting pad and flywheel face if its locked in.
@shucker1
Very good advice! I'm too old to think of everything anymore!
The front pilot hub on the converter is soft, not hardened, while the crankshaft is quite hard, and gouging of the edge of the hub can indeed make it difficult to enter the crank, giving false impression the converter is binding in the pump. Then, there's rust and corrosion, sometimes. I always like to take the converter in hand, and "feel" the fit in the crank before assembling. Once assembled, you should be able to rotate the converter by hand within the clearance of the mounting holes to check freeness in the crank, nice to do, but important only if you need to rotate the converter to "find the holes". Usually, my experience has been the studs enter the flexplate before the hub starts in the crank.
FWIW, this is vastly different than a manual transmission input shaft pilot locating in the crankshaft, because the converter never "rotates" with respect to the crank; they are locked together. In the manual set-up, the crankshaft spins about the input shaft, which may be standing still with clutch released, in gear, at a stoplight. Everytime a shift is made, a certain amount of spinning occurs between the crank and input shaft, while the clutch is released. When engaged, the two spin together at the same speed. So, the input shaft is both supported, and provided with a bearing in the crank.
As a young guy, teens, deeply into messing with my Mercury (1955), I was driven to learn and understand how all these parts worked in relation to each other. Today, my wife knows that, and says it drove me nuts! imp