17.5T brushless is around the old 27t brushed and 13.5T brushless about the old 19t brushed. So you are probably looking around the 9.5T-10.5T range for those motors.
Brushless work better with Lipos and most brushless ESCs work with Lipos.
Yes run sensored.
10.5T or 13.5T brushless may be better as some vintage classes have motor limits and you may want to race it
