I'm wanting to grab another "dummy plug/oil pump drive" and/or cam position sensor/oil pump drive plug on my next junkyard visit. I know on the 2.9 the fastening bolt for the distributor is a 13mm head - is the 4.0 the same?
Visited the junkyard yesterday and so I can now answer my own question more definitively. The hold-down bolt on the 4.0 is actually a 10mm hex head. On two different engines I was able to use my Gearwrench box wrench to loosen the bolt after clearing some stuff out of the way (wiring harness, transmission diptstick tube, etc). Once cracked loose, a stubby Gearwrench would have been a nice bonus as the swing angle is rather limited and the factory threadlocker prevents you from just spinning the bolt out with your fingers.
No way are you getting to this bolt with a socket - there's just not room - even my Gearwrench was a snug fit. A 10mm distributor wrench might be a useful tool to crack the bolt loose, but it's certainly not required.
I trashed the electronics portion on one of the parts I removed due to the thing being somewhat seized in the hole. Not a big deal as I don't plan to use the cam sensor output, just the physical drive-gear portion.
Both engines I worked on were OHV. My quick assessment was that it was easier to get the drive-gear out of those vs. the SOHC engines.