i have around 6 1/2 inches to the bottom of the fork where the bottom bearing is to where the nut is. It is threaded also, the one i got the threads where way too high up for my bikeSpacers work great if you can't get an exact fit. You have a threaded headset so that might be the quickest and cheapest route to go. My threads were over an inch too high so it would have cost me around 20 bucks in spacers or for them to cut it down and thread it further. I went across the street to a machine shop and had a spacer made for $10.
I already returned it today in fact i'm doing my research at the moment for another one that might just work im asking the seller for the thread hight from the bottom to the bottom of threads it says Steering Lenght 7 3/4 in and Threaded: 3in so it should go down to a 5 inch steerer tube https://www.ebay.com/itm/TOP-GUN-Fo...ver/232857510336?_trksid=p2485497.m4902.l9144Are you able to return the forks? Steer tubes on forks come in different lengths and how far they are threaded. You could just exchange them for the proper length or switch to the threadless forks but you'll be into a new head set stem and the works. A spacer is your easiest option if you don't want to return them.