Remember also that there are TWO DIFFERENT Pilot/spigot bushings when dealing with Mopar engines...
Typically as a rule of thumb, if the engine came from in front of an Automatic, you will need the "Conversion" bushing, if it was a standard shift engine from the factory, you will need the standard bushing..However, I have seen where this wasn't always the case, as some are vise versa...There is only about .030 difference between the two bushings....I have tried to turn down bushings, it doesn't work very well..I've seen this done with anything from a lathe to a drill and a flat file...
Here's a helpful hint: ANY FORD, or CHEVY STRAIGHT DRIVE engine has the correct thread and grade bolt that WILL WORK in a Chrysler engine...There are even 6 bolts too...How do I know this? I'm running FORD 302 Flywheel bolts in my 440 4-speed car today...I have also tried CHEVY bolts and they work as well....