jovani
True Classic
Your discovery is correct, although double raw might be too much for the water pump and frankly is not necessary. I thought about about this conversion 17 years ago when I had my second X1/9, but built it on my hand made Alpine A110 replica instead, which has similar front end bottom. I used radiator from Audi 1800cc Turbo.The reason I did what I did now is result of circumstances. My X got stollen and I found it a week later with a hole on the radiator and ordered aluminium replacement the same day from Vickauto. When I got it, I just made backside duct with the idea to "flatten" the boxy parachute area by reducing it's hight 4 inches and guide the air down/out around shorter and angled plane instead of tall and vertical. The other idea was to make everything reversible to original in minutes with no traces of the conversion. All this can be done even sleeker and easierI found by tilting the radiator rearward like this, it allows for a taller unit to be used. Comparing the VW radiator options, the smaller versions are about 12" tall...which is about the maximum that can be fit is the stock "forward tilt" position (and even then it sits a little low on the bottom). But with the "rearward tilt" position a 13-14" tall unit will easily fit and puts the bottom of it higher up for added ground clearance. This allows use of the much larger capacity 2-row rads from some Dasher/Passat models.
Seems like your modification to the air duct behind the radiator ("45 degree outlet") would work well with this rearward tilted mounting position. Any photos of that panel behind the rad?