if your getting high temps its going to be headgasket, worse case head is cracked

the white smoke your seeing is steam, so if the head gasket is split or the head is cracked its allowing water into the cylinders which is being pushed out into the exhaust causing the steam, but if you let it get that hot becuase the head is alloy it warps the head and you can only take so much off before the head is scrap anyhow.

dont run it up anymore, get the head off or take it to a garage to be sorted, becuase water doesnt compress so your causing more damage by keeping it running

another thing to check is your dipstick and oil cap, check to see if you have any white sludge in there or on dipstick, becuase this will show water in your oil which isnt good either becuase the water will get into your engine and then cause a lot more issues

the cheapest if just a headgasket in what you need is

headgasket and top end gasket set
headbolts
cambelt
may asel put a tensioner on aswell
spark plugs
oil and filter
may aswell do thermostat aswell while its all off
head skim and pressure check

if head is scrap then new head, you can use your cam and lifters from your head anyhow, or replace with a higher lift cam while its off