My old 300 diesel had mechanical linkage that actually got a little bent where it runs through the firewall (and subsequently hung up), which caused a pedal so stiff that I acually broke the top half off after about six months. I had the linkage straightened and lubed and put a new pedal in and all was well.

Don't know if the 300 is a mechanical linkage system but may be worth looking into as leg cramps on long trips aren't much fun.