After responding to your other post last night I remember the important thing on converters using a mid plate is to make sure the converter hub on the block side of the converter fits into the crank hub snout properly.
Your back spacing on pump engagement is probally fine
( No it is not
, it needs to be deeper on second thought
)) I use a straight edge laid across the front of the tranny bellhousing area and I measure to the converter mounting lugs, if it is between 5/8 and 13/16 deep I'm good on the converter installation into the pump
How thick is your midplate
Which brand converter is it? I've seen several race converters that the converter hub was to long , they would bottom out in the crank leaving a gap between the flex plate and the mounting lugs
Those guys used one hardened head bolt washers between the mounting lugs and the flexplates to take up the gap, my concern is the converter bolt length having enough thread engagement to be safe
I just reread your post, make sure the converter drive hub is all the way into the front pump
It should be deeper than 3/8 from the tranny bellhousing front mounting surface
