We have totally desmogged Landcruiser engines (I mean 1,000 percent), particularly when testing the fuel injection system. I can guarantee you the desmogged engine runs just fine and you are it's best new friend. We actually use 1/4"NPT plugs in the head at the air rail. I'd probably want to trade that massive Exhaust Manifold for a Header. I'm not sure how well a desmogged factory carb runs because I've never done it (I'm not one of the guys on this forum that buys into use of factory carbs). The factory carb may work out just find, I'm sure PinHead would have more information on that.