The blokes in the UK (LS1power) who were pioneering the P38A LS1 transplant actually matched the LS1 engine to the rover ZF transmission using a specially cast bellhousing which then required specific machining. On their original (but now defunct) website, they reported using all the original rover/Bosch etc sensors /electronics so as to retain compatibility with the BECM...I guess this would include crank/cam sensors as well as the throttle positioning sensor. The final product was then converted to run on lpg!

I was able to email them just before they closed up shop...they explained that they had a pile of bell housings needing machining ---I suspect they ran into cash flow difficulties...bloody shame...maybe we need to sponsor their emigration here!