You betchum, Red Ryder-
In spite of the shadows, the ghost pattern sure looks rattler-ish!
For a snake THAT SIZE the strongly keeled scales it exhibits are shared in the pines only by pinesnakes and northern watersnakes. A number of smaller species also have keeled scales. If the head skin is available, check the skin between the eyes. In the timber rattler and copperhead that space is filled with very small scales - much smaller than those over most of the body; in pinesnakes and watersnakes the interocular (top of head) region has a few large scales/plates arranged in a symmetrical pattern. If the head is absent, but the tail is still there, check the ventral scales/scutes caudal to the anus. In the pinesnake and watersnake (in fact in all NJ snakes other than the pit vipers) there are two rows of "ventral caudal scutes/scales" behind the anus. In the rattler and copperhead (and massaugua... I think) the scales behind the anus are in a single row, just like those ahead of the anus under the belly.
As for estimating the size of the snake from a complete shed skin ? Hard to do with any exactitude. Generally a shed skin, because of scale overlap in the live snake, will stretch another 20% to 30% of the live length.
For more info on scale counts - the most accurate basis for identification - check any good field guide to snakes in the region. The best, IMHO, is an oldie but goodie by Roger Conant, former Curator of Reptiles of the Philly zoo - I think the title was "Field Guide to North American Reptiles and Amphibians". I'll bet that copies are still available on ebay or thru abebooks.com
Nice picture, Bob !
Dave