I've seen more than a handful of OHC motors sitting in PV engine bays. Upright mounted. Although they look bigger, I don't think the OHC motors are really any taller or longer than the B20's are. And if you pick the right B230FT, it is probably a far cheaper path to 200 - 250 hp than is the B20. Because it can be done on a largely stock shortblock. By the time a B20 is making that sort of HP you are into serious money with modified heads, superchargers, etc. But getting a B230FT to there costs only hundreds, and the parts can come from junkyards (truck intercoolers, later model Volvo turbos).

I'd imagine you main problems will be:
1) Exhaust side: the PV has a rather narrow engine bay down low. those big frame spars rise up near the back end and fit somewhat snugly alongside the engine. Might need to have some carefully crafted downpipe, possibly even a custom built exhaust manifold to position the turbo where it isn't hitting anything.
2) Intake side: The intake manifold will probably want to occupy the space where the heater currently is. You could remove it, and use a more compact hot rod under-dash heater system and open up all that space under the hood.
3) Ignition (also a problem on 240/B230FT swaps) - later model 700/900 series turbo motors have crab distributors on the back of the head, you'd probably need to swap that for a block mounted style.
4) FI/ignition control: Just megasquirt it. Frees you up of all the constraints of a black box OEM injection system. And you are then free to make modifications to the motor as you see fit without Bosch disapproving of them.
5) Trans: As an initial step, you can just use the PV's trans if you want. Once stood up (use a B20 oil pan and pump, I think) a B18 bellhousing will bolt to the OHC motors in a normal fashion. If later on you blow up the trans (which will, IMO, be more an effect of the tires you use than the HP rating of the motor) then you can think about getting something stronger on it, with (probably) custom driveshafts. In a PV, nothing but a plain long shifter-ed M40 will fit without chopping out the tunnel to make more room. M41's require surgery, as would M45/46/47 (for the shifter position as much as anything else on the M45/47). If you are making epic amounts of HP and running sticky tires and munching M40's, you should probably go to a Mustang T5 swap anyhow, and swap the rear end while you are at it.

My PV has something like 170 - 175 HP, which is pretty fun for a 2200 lb car. That's with a lot of mods on the motor (actually, very little totally stock and unmodified components are on the motor). But with my 245 and it's cheaply modified B230FT, I've seen the dark side, and I like it. The wagon is probably closing in on 250 WHP, and that's with a totally stock late model B230FT motor (It's a '93 940T motor), with around $1500 in supporting mods (3" exhaust DP to TP, 16T turbo, ported turbine housing and exhaust mani, IPD turbo cam, MSnS, Isuzu NPR intercooler, Ford browntop injectors). Even though the wagon weighs in at 800 lbs more than the PV, I think it's quicker already. And quiet and civilized at the same time.
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'63 PV544 rat rod, '93 Classic 245 + turbo