I am considering purchasing a 10x14 springbar tent but I have read somewhere that tent pads in National Forest and Park sites east of the Mississippi are smaller than that in most cases does anyone know if that is true

I would say only a small percentage of NF campgrounds have tent pads. In most cases, you plant yourself within the invisible boundaries of the campsite. I can't speak for national parks. In the event the pad is a bit smaller then your tent footprint, I don't think the Forest Service will care if you overlap a tad. If you click on the "National Forests & Campgrounds" tab to the left, you'll find campground descriptions, which indicate whether there are tent pads.