Yep, the steady rests are replaced by the new ones built into the headers. I had my doubts, but have had zero problems AND no leaks. That's right headers without leaks.
On the master cylinder-it came with my disc brake kit. I did run it at first with the stock exhaust manifolds and never had a heat/brake issue and I drove it all the way to Columbus and back one year. But I wouldn't guarantee this idea seeing how the stock manifolds do generate more heat. Now tho the headers dissapate heat very quickly and let the engine run a little cooler, like you suggested.
I also have Flowmaster mufflers mounted further back than the stock postion. This helps to keep your feet cool on longer trips in the summer. I highly reccomend this idea and come to think of it I should post some pics of how to do it.
The oil filter is in the stock position, I have yet to remove it successfully without spilling oil on the collectors. So more cleanup is usually in order. I don't think you could use the right angle mount with them, but it might work. I was considering a remote mounted filter actually.
A L A N F R A K E S ~ Tulsa, OK