mack r series with 425 tires, poor turning.

So I've got this new to me mack, r series with a national crane on the back. It came with 425's up front, but it won't turn for squat. I made a 5 point turn into hardee's on the way home with it (and that was a fairly wide driveway). The axle stops are adjusted correctly for turning, I removed the floats and put a set of 24.5 lo pro up front, and adjusted in the stops, and that made a world of difference, but I've lost all my weight carrying capacity. (I was just messing around at the shop and had those rims around with tires on, and wanted to see what I could do.) I'm probably around 16-18,000 up front. (I need to go scale it yet). I could go to 315/80 22.5 and get back my weight capacity, and still have a narrow tire, but I'm wondering if I can just space out the front rims further, and keep my 425's. I've looked for a little more offset in a rim, and can't find much available. The current rims are budd/ stud pilot, not hub pilot. Right now the floats hit on the pitman arm coming off of the steering box, the narrower tire helps me with clearance there. I know that I'm fairly long wheel base, but with the floats on, I can't even make street to street turns without being in the ditch, or stopping and backing up again. I thought of just getting the longer studs for use with a aluminum rim, and making a 1" spacer and seeing where I'm at.