My name is Christian Ray from Omaha, Nebraska im 18 years old and have a love for the mach ones. I just purchased my first Mach 1 its a 1973. It is white in color (has been repainted) i plan on returning it to the original pewter silver. the car has the original 351 cleveland but it is rebuilt with a hotter cam ported heads 4 barrel carb and different rear gears. The cam is from cam research in denver. in very excited to start the restoration my first project is to get the speedo working correctly. then i will put new exhaust, new drivers seat because original owner took out the original seat and put a aftermarket seat in, install new radio. new dash pad and last but not least paint!!
Glad to have you here with us. I can read your excitement between the lines of your post! The Pewter Silver is a great color. Mine is also currently in a re-paint white (originally light yellow) which I hope to repaint in the medium yellow.
It will be interesting to hear you thoughts on the Cam Research cam.
GXR has accurately answered your first question. You just need to change your speedometer gear.
As for a set of stock front seats your best option will be locally through either a salvage yard, or something like Criagslist. I am sure that Don Whit at Ohio Mustang Supply will have a set and can also set you up with new upholstery but shipping will play into the final cost.
It's a pity I am down here is Australia because I have 2 complete sets of high back seats to get rid of! Actually, Dad and I have an entire shed full of parts from a '73 and '72 to get rid of!