One more thing that should be updated is the info for the M50D-r1HD
The r1HD can be bolted to a OHV and SOHC 4.0, but the r1 cant be bolted to the SOHC. There is an extra bolt hole on the r1HD that allows it to be bolted to either transmission (at the 2 O'clock position).
You can see the there is an extra hole (top left) to accommodate both 4.0 bolt patterns
This is the back of a SOHC 4.0. Towards the right of the centerline of the block, just under the passenger side head there is a 'blank' spot.(this hole would be tapped out andused on an OHV)
Here is a pic of the r1HD bolted to a SOHC. You can see the extra bolt hole for the OHV pattern in this pic.
-plumcrazy