You can use alle the original sensors, but if you want to do the best for the engine then minimum buy a 36-1 cranck wheel, use the one from the t25 and use the std cranck-sensor also, all works just fine with it.
This setup you can run semi sequential with and if you add the cam sensor from the t25 also then you can run waste-fire or full sequential on ignition also.
The new haltech E11 can also run std cosworth setup 4-2 tooth, they have build that into the software now