i have a 68 gto factory a/c car.i decided to rebuild original 400 with a crank kit(basically a 455).engine has about 1500 miles on it.i have delo 15/40w in it now.after doing some reading i was thinking of going to 30w vr1,etc?i live in phx,az so the temps are 100 plus now til mid sept.car without a/c on runs around 190/200 depending how long i sit at a light.with the a/c on engine sees 220 at long stoplights.will 30 weight be able to handle the heat of the engine and enviroment i live in?it's my weekend cruiser and when it gets cooler it will be going to the track.i flog it every chance i get when i take it out cause it's just a torque monster and it doesn't take much to beak the tires loose.it has a flat tappet hydralic cam.no oil cooler.high volume/high pressure oil pump.should i try a good 30w or stick with good ol' 15/40? if i was going to use 30w i was going to use a straight weight.i know there are two different camps on thick oil versus thinner weight oil.right know i'm on the fence on this one.i value your input and thoughts on wether i should try 30w or not.