You'll have to add sensors. I've thought about this a bit lately, and I'd really like to see flow statistics to make sure the pump is even running. I lost an engine on my '90 when the 185cs pump failed, so you could say that I'm a bit paranoid about this sort of thing
I would think the best place to run sensors would be on one of the lines as close to the core as possible.
Anyways, on to the other issues:
For the heat exchanger, if you fancy your junkyard luck, others have managed to re-purpose a Fiat Cinquecento radiator.
My 205 h/e was leaking this summer, so I actually considered that before buying the core that gt4-play sells. The nice thing is that they also sell silicon hoses for the system, and they were pretty affordable @ ~65$ USD for the set. The factory routing involves a fair amount of bends and tight angles. There are normally some hardlines that help out with this, but if you pick up their silicon hose set and a couple of couplers, you can make it work without those hardlines pretty easily. The pipes and hoses are 22MM (7/8th inch) ID, so.. it's a pretty weird size to work with here in the states. I wasn't having much luck finding anything except couplers and just straight 7/8 in hose on amazon.
gt4-play also sells reman pumps, but I think they require a core. You could see how much they'd want without a core, tho. Otherwise, you could probably get a universal pump to work. I haven't looked into it yet, but it shouldn't be too difficult I think. You'll have to let us know if you have any success there.
best of luck!