RE: lookin for new speed plane
Any of those aircraft can easily handle the ST90....
However the combinations will not be particularly fast. At least the P-51 and King Kobra have the potential to install retracts.
Yes, they all will move along nicely ---- you will have to define "fast" for yourself.
With the ST90, I'd say the king kobra is the best bet to keep you happy, from your list. Similarly along those lines, look for any of the 1970s and 1980s type pattern ships. For decent speed, retracts are a must. Take a look in the Classic Pattern forum for some ideas for planes like this.
Great Planes Patriot XL is worth considering as well. Perhaps the Cermark F-16 and new F-18 too (you would want to at least add a tuned muffler to give reasonable performance)
other mentions ..... World Models Midget Mustang. Perhaps the new Kyosho Kelly or the Cermark Alley Cat. We know the AlleyCat and MM fly nicely with a Jett 90, so installation is possible - no reason they shouldnt work with the ST90. Not sure on the Kelly yet, but its looking hopeful.