If you wish to use the HO's head and intake, the Renix TPS must be adapted to work on the HO TB. You also need to swap the MAT sensor onto the HO intake. The EGR system was removed in 91, and it will not work with the HO intake manifold. The function of this system was compensated for in other ways including the camshaft, so the HO engine does not need it to reduce its emissions - however good luck explaining this to the guys if you need to pass a visual inspection. Removing emissions equipment is illegal everywhere, and logic has little to do with law. If you have any doubts about being able to get away with this, just swap the head/intake, doing so saves a lot of other swapping work as well. (it's funny that I learned all this on here, and for whatever reason people care now. 4 years ago the removal of emissions parts seemed like common practice on here)
If you do use the HO intake, there is a TPS adaptor available from Hesco
http://www.hesco.us/shop.asp?action=details&inventoryID=45563&catId= or you can make your own. There should be some threads on here about making your own. The Renix exhaust manifold must also be modified to work in this case, as there is a hole in it for the EGR tube. It might be easier to make the HO header work, but I didn't try this. Regardless of exhaust manifold, the intake/exhaust gasket needs to be for the intake/head being used.
There's a bunch of other stuff, yet still easier than swapping harnesses. You need to use the Renix's alternator. Regardless of which intake you are using, the Renix fuel injectors need to be installed in it. Yes it will run with HO injectors, but you will get crap for gas mileage. As stated there might not be a hole for the knock sensor, and if there is it won't be threaded. If you can figure out what size the threads are(not a common SAE size) then you can tap it. If not you can just hook the thing up and hide it somewhere. I've heard you can actually just remove it, but I've also heard that it needs to be plugged in so mine is plugged in. There is a temperature sensor in the Renix block, and there is no hole for this in the HO block. This sensor should fit in the HO's thermostat housing. This is the sensor for the ECU. The Renix, and some HO's(I think all OBDIs), have another temp sensor in the head, this is for the gauge. I don't know if the sensors themselves fit in eachothers' holes, since I just adapted the wiring and hacked my cluster to make the HO's gauge work. You will most likely want to try to switch these sensors if possible. You also need to use the Renix's distributor, and the sensor that is in it. The other CPS, the crank sensor, must be swapped to - no matter what year transmission and engine are used, the CPS and the flywheel or flexplate used must match the engine electronics used. Therefore, if you are using swapping transmissions as well, you must swap the flywheel or flexplate if you are running Renix, and likewise, if you are switching to OBDI, then you need to find said part from an OBDI vehicle.
No, it is not a direct bolt in even if you do it the easiest possible way.
I'm sure there's other things I have forgotten to mention. Basically everything with a wiring connector on it needs to match the ECU being used, even if it doesn't seem like it would.