I wouldn't worry about it. Ask the folks at BPE about them.They sold them to you. Those guys & gals are very knowledgable about thier parts & will explain any worries that you have.

Cars with low gears on the street would probably benefit from those pulleys especially being that the coolant will slow down enough to absorb heat instead of flying by at a higher rpm
That's why the circle track boys run a setup like that