The MAP sensor that I have is off a Ford, I got it from a friend at the shop that does the work, it just needed some wiring adjustments but otherwise not too much work to put it in.
As far as the pistons and rods, you'd probably have to upgrade the fuel injectors if you haven't already. prob some mitsu 440's or something. If you just do pistons and rods, I would say you could make it to around 300 or so, but our sleeves are made out of a cast iron which are incredibly strong! which is good. without sleeves though I would be careful due to the open block design and watch for sleeve walking (where they move around) maybe get a block guard (around the sleeves to be safe).
If your sticking with the stock head I would go ahead and upgrade the valves, valve springs and retainers too, for a higher rev and more stability....
hope that helps, let me know if you need any help whatsoever!