Nice to see someone thinking of trying something different. IF you have the place, equipment, ability and money to do this. Definitely not something you want to pay someone else to do. Unless cost is not an issue.
Why a TDI? The fact that you already drive one isn't a compelling reason. More of a "that's what I'm familiar with" thing. Not the best way to choose what motor to use.
First problem I see is that most of the gauges in a 99 ZR2 are fed their info from the PCM. By using a stand alone on the engine you'll be leaving them blind. You need to get hold of a complete 99 ZR2 wiring diagram to see how a lot of the systems work. 98 up S10's have a fairly complex integration of various modules. Not like a 2018 vehicle by any means, but it has multiple inter dependencies.
Give Current Performance (CPW) a call and see if they have any suggestions.
Yeah these swaps are definitely time/labor intensive, and not cheap. I think the guys on the TDI swapped Trucks facebok page say their average costs are about 10k. Considering a new diesel ZR2 Colorodo is about 5 times that, id say its worth it. Plus you cant buy small trucks anymore in general let alone a diesel, which blows. There are a few s10s out there with ALH engines in them in Canada from what I've seen but details on things like weather they used the VW cluster and just shoved it in there etc. are sparse. Definitely not going to be paying anyone to do it though that would be financial suicide haha
I have several reasons for wanting to use a TDI, but the main 3 are power density, power efficiency, and reliability. Sure I could try to do a 4bt or similar, but that engine is massive both in size and weight. To build up that engine would probably also be expensive, if there even is a way to tune or modify them (I don't know). In that scenario I wouldn't net much fuel gains either due to the extra weight. The TDI is a tiny little motor that can be setup to produce gobs of torque with just software, Its lighter than the 4.3, and its diesel so its inherently much more efficient. Most guys are claiming low 30s for their mpg's in tacos and other 4x4 trucks, which I definitely believe (I get almost 40 in the Passat with a manual). I have to check the stickers on both but the s10 only weighs a few hundred pounds more than my Passat as is, so that gives me a good frame of reference for how it will perform with the slight extra net weight.
I'm not looking to have a race truck, if that were the case an LS engine would be my choice. I want an efficient little work truck, that I can use for around the house/to tow small trailers every now and then. With the increased torque I think it'll be quicker/more fun than stock anyways.
I have a Hanes manual that has some diagrams but I've been searching through here and other sites to find high res PDFs of everything, I have to organize what I have and start going through each system independently. The good thing is that I have my old 01 Blazer still that i ripped the transmission out of and stuck in the s10. I can use all the wiring/systems from that to test on a bench, and verify that stuff works before the final install.
I took a look at CPWs site, I'm wondering if they would so something similar to what they do when you use a LT1 engine on a 98+ truck
From their site:
"The trucks that came with a PCM mounted on the overflow bottle under the hood will require both the stock truck computer and the ECM from the engine IF you are installing an LT1 engine AND you intend to keep all of the factory truck functions......When complete, the stock truck computer will control things like the cruise control, ABS, speedo, etc. The computer for the engine will pretty much just run the engine and control the electric fans."
Knowing the I/O from the VW ECU, maybe with a few data converters/transducers, a similar setup can be had.