Check to see how thick of a plate you can use for a bulkhead mount. Using bulkhead style and snap rings, I'd want as thick as it will allow.
Then price a 1-1/2" drill bit. Do you have capability to drill some holes? Or at the very least, get the metal, pilot all the holes with a 1/4" bit, and swing by a machine shop. I can imagine it would cost more than $25 to have the simply drill a few holes.
What valve did you get from Baileys? If you got the same chief I did, There is no directions as to where the PB plug goes, but there is only 1 port it fits in. And I didn't mention it in my thread, but the PB plug was just a hair too long. When torqued in, it bound up the one spool on that side. No big deal, just shaved .010" off on the lathe. But could have easily been done with a file, grinder, belt sander etc. So just something to keep an eye out for. Same with any valve really, once all your ORB port adapters are installed, make sure all spools still operate smoothly. Which is why I install the fittings on the bench before mounting everything