1 inch steerer tube

Can someone tell me if the outside diameter of a 1 inch threadless fork is the same as a 1 inch threaded (not the threaded part of course). And, is this the same as 1 inch mini? Long story short I am trying to put together a Redline Prostyler and I dont have the long forks to fit the 5 inch head tube on the frame, so figured it would be easier to use 1 inch threadless till I find forks that fit

Thanks.Loren