mechanical to electric fans

[pandrade]

one of the first things i did to my supra was upgrade to a 3 row aluminum megan raceing radiator. i used a 89 fan shroud which allowed to me use its 2 aux fans versus my oe 87 which was a singe. all this and optimizing the water mixture keeps me cool at all my races and daily No problem.

i want to make a little more power and increase efficency and thought if i get rid of the bulky mech fan might free up bout 10hp and the added benifits of beter efficency, cleaner engine bay, and alot easier to change belts, my mechanic has taken charge of this project since i dont know crap bout wireing and we are hooking up a 2 speed electrical fan from a 5.7 durango and it fits perfictly( he has been raceing since befor i was born and custome building all his cars) he tells me the wireing is easly done since he has all the controll relays for the fan. the whole time he is giving me all the parts and ALL labor for 45$ since our familys go way back

my question is what temp should i set the relays to( he knows what he is doin perfictly i just want to better inform my self) i was thinking 100 for low speed and the high speed to kick on at 120. Your thoughts?