Thanks CM: Its a motor plate, Rb Block/727 /8.75 combo.

at this point, it looks like i'm either going to be fabricating a trans mount and keeping everything a little further to passenger side ( if headers will clear ) or, have 8.75 re-cut.

Going to hang plumb bobs and see for sure- cannot find a spec for where the dang third member centerline "should be" from spring perch's.

Thanks for the help.