I would mock it up in the chassis and have the trans mount/crossmember bolted up tight in the frame rails. then fit those mounts and see where it sits.

IIRC the difference is in the trans mount/crossmember location in the frame rails with a 4x4 sitting a little further back. why those mounts are offset reaching forward.

2x chassis trans sits a little forward and why the BB mounts are straight.

my 2x mounts were made from 2x4 tube stock cut/drilled copy of a stock set. so you very well could do some drilling/milling to make them work.