Outer Limits 4x4 Board

just wondering what the heads on an 3.5 dohc are like for corrosion and whats the best coolant to put in these motors

Like any alloy head it will corrode if you don't change the coolant regularly. use a longlife coolant that way you only need to change it every 4 years. I use Nalcool long life and mix it at 33%. I've had the car for 5 years and had no problems yet.

flushed it out on the weekend via the heater hoses but didnt do the blockgave it a good flush but i have a funny feeling ther wa still green stuff in the block does it matter that much a bit of old coolant they say it is not good ,what do u guys think

If it were mine - i would be doin it agian to insure it's all gone. Its not a myth, diff types of coolant mixed together, be it the smallest amount and one of both of a few things a very likely to happen. Jelling of the coolant, rust inhibitor can actually turn corrosive, boiling point lowered, freezing point raised etc.

Wouldnt ya be pissed if something were to happen costing possibly thousands over $40buks of coolant??

I Don't think it will be a problem having a small amount of the old coolant in the system. Maybe run a radiator flush through the car before you put the new coolant in. Coolant manufactures normally recommend this process anyway.