So here goes, I went to install my sm420 into my 400 small block today and thought i had the splines lined up on the tranny and the engine, i had the bolts in it and was tightening them down, when all the sudden a pop occured and the bell housing cracked in several different places. What did I do wrong? Is there a trick to getting it lined up? And what things should I be worried about since the bellhousing is cracked. I am used to working on motorcycles and just started messing with vehicles and this is the most extensive thing i have done to date. Also will any bell housing work as long is it from a chevy small block? Thanks for any help.