Hello Buzz....
Most of my favourite aircraft in my FSX are FS 2002/FS2004 types, and they mostly appear, and perform OK!
Just remember the installation procedure in FSX is the same as FS 2004, except that now the aircraft are directed to the; "SimObjects" folder, and installed under "Airplanes", "Rotorcraft", etc, etc...
If you do all that, in the same sequence as you did for FS 2004, after reading the"Readme" file in included with the download, everything should be OK!
The; "previews" in the list may look a bit odd, but the proper models appear OK in the Sim!
Have fun with your FS 2004 downloads!
Paul....

...!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.