Helped trying to fit similar carbs to a polo 1275 lump before (more pain than its worth but....) and you really want a bike fuel pump from a similarly sized engine and to blank the mechanical one thats driven off the cam. This was the first thing that caused fuel to pee into the inlets! (You only need about 7psi fuel pressure) The next thing was getting the floats to seal properly and to get this we ended up having to shim the float needle as the floats werent easily adjustable without breaking the springs. Without showing you pics of what we did its a bit difficult to explain this though lol. The next thing that caused this was air leaks between the carbs and the inlet manifold. This caused LOTS of problems as it was a nightmare to seal the inlet due to my friend who's engine it was being VERY pikey and refusing to spend money on some decent hose lol. Never did figure out why this caused so many problems though although the way we had them to make them seal made them essentially pretty solidly mounted to the manifold, if we made the connecting hoses longer to give some flex they leaked.
1.5mm is definately far too big for the mains from our experience although I cant remember exactly what they were running last time it was on the road. We ended up buying some jet drills to set the jetting for much cheepness, if you go too big and need to go back you can solder the jets up and re-drill them if needed. We didnt have too many problems with the angle of the carbs but that may just have been the angle that the polo engine was at was pretty similar to the angle of the bike they came off (we had no reference though so I wouldnt know lol).
The one thing I did get out of all of the experience with this guys car was never, ever, ever! to bother unless I had the budget to set the car up on a rolling road as getting all of the jets, mixture screw and idle screw to work together was a complete nightmare that, even with a proper exhaust gas analyser and a wideband lambda sensor and logger unit plugged into the exhaust we never got the things anywhere near what I would call well set up (the owner liked to kid himself though so who was I to argue lol, it was his VERY LARGE fuel bill after all lol). Learnt a lot from the experience but its definately not one to try on a budget, it just doesnt work lol.
If you do set it up on a rolling road (and find someone who will do it for you!), get a spare set of jets and some jet drills as that will save you a lot of time finding and buying new jets, you can alter the spares if the ones that are in there need it while the old ones are swapped out. Should save you a few pennys on setting up time.
