For the surge tank separation, I'm thinking of something different then what I have been reading on this forum.

I am considering buying a stock MB or BMW surge tank that is inexpensive and retains the stock look (not one the size of our stock tank but a small one that will mount next to the radiator on the shroud) and use it for the radiator overflow/surge/fill tank.

Then keep the stock tank for the HE. While this is not the trickest race proven way to go or will it add more capacity - it will separate the two functions and allow me to use a different fluid mixture for the HE. This, and a larger HE (increased capacity and cooling) along with a better pump and a cooler thermostat should help to reduce/maintain the IAT to best/decent performance levels without a lot of re-plumbing or losing battery/cargo space.

Just my .02c

These are just some examples:
http://www.bavauto.com/fland.asp?par...07%20787%20039

Here is a nice A/M tank that might mount on the radiator
http://www.cantonracingproducts.com/...ion_tanks.html