AHU - spacer behind flywheel?

[Smoker]

I'm putting together an ahu that's been sitting in my shop, partially disassembled, for a while.  When I attempt to bold the flywheel on, it makes contact with the plate/guard/whatever on the block.  What am I missing?  I vaguely remember something being behind the flywheel, but I have no idea where it would be...  help?!

[vanbcguy]

There is nothing behind the flywheel on my AHU....

I'm using an aftermarket South Bend flywheel though. Not sure if that makes a difference. Definitely not contacting the plate on the block.

[G60ING]

I ran into this same issue about 6-7 years ago. I was installing a eurospec light weight single mass flywheel on an AHU for a friend. I had everything assembled and in the car and it wouldn't rotate. I pulled it back apart and ended up installing a 020's shim so the flywheel would clear the backing plate. What a PITA, GRRRR

here is the new flywheel that required the spacer vs the old one: