Don't get too caught up in the MPH wars..many of the speeds quoted are just guesses. Get a good quality engine, set it up properly, and you will go fast.

I think the GRRT will go fast enough to smoke your Shrike guy...read some of Andy Steere's GRRT numbers...that is cooking pretty good.

The Jett FIRE 50 will, too. This engine on a 9X10 will give you plenty of speed, Dustflyer has one on a DDust with this combo, and it hooks.

If you have to ask about the header on a Nelson FAI, then you might not be ready for this class of engine...the pipe is coupled right to the engine (and it is on the GRRT, too, but..) and these are not easy to tune sport engines...they are so much more finicky than anything else you have mentioned..FAI pylon racers carry a box of props that are just a minute amount different from each other, and a box of head shims of different thicknesses, just to tune their engines from day to day. And they don't have carbs..just fuel shut-offs. And they use a special ($$$) glow plug, can't just slap a long Fox in it..These are extremely complex designs made for all out speed. This, and the fact that the props they must run give very little static thrust on take off (remember the take off questions??) would make for a plane that wouldn't be very easy to operate. But if you ever got it tuned and in the air it would outrun a Shrike.

Even the OS fan engine I was running was pretty easy to set up, and again the pipe was hooked right to the engine.

So my advice is to not get too wrapped up in being the fastest thing on the planet..just get a good, reliable FAST set-up and have fun!