Indeed. Almost all 1800's had OD's especially in the US. But if one blew up it's certainly possible for someone to have replaced it with an M40.

I'd jack it up (securely - safety, safety, safety!!!) and check both for the presence of an OD. The front section of the driveshaft probably isn't swappable (at least as far as I know) so you'd have to have the 544's shaft shortened. During that process you could use the front fitting off the 1800 shaft if it isn't the same as your PV's, to avoid doing the flange scavenger hunt across the internet.

And if you want a short shifter in your PV, I'd think about grabbing the whole tunnel too. Might be a little snug up against the hand brake, though. I used a 122 tunnel in my swap, and retained the long shifter. However you do it, there's a large hole to be chopped into your PV and refilled with new, roomier sheetmetal.
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'63 PV544 rat rod, '93 Classic 245 + turbo