The hard part with the cooling isn't getting the iron to cool off, it's getting enough water through the block and passages to cool effectively while at the same time still having the sleeves perform their job. I think the darton sleeves have a block guard built in, are rated to 20 PSI, and have some of the largest water jacket cutouts available. Couple that with a brand new water pump, an extra hi-flow hayden fan on the front of the radiator [or one on front and one on back], and you should be fine. Air speed across the radiator is what keeps the water cool, so you're going to need some way of making your own air speed when you're not moving