[Speedbumpauto]

From my perspective, I absolutely would not do anything more permanent than you already have before you fit a bed on that frame. IMO, the wheelbase dimension is worthless when you get to the level of modification you're at. What matters is the wheel centered in the wheel well. Another thing to consider is the 1" DOM tubing is readilly available and easily cut and tapped. The TCI guys will possibly trade you for the length you need IF you end up needing it longer. The last thing is to remember those bars/brackets are only in compression and tension which makes them stronger than they might look. One thing you could do at this stage is fabricate a crossmember in front of your forward brackets. This will decrease frame movement which could induce torsional or lateral forces on the bars which is where they are not strong. I did a crossmember and even triangulated a couple of brackets up to the frame(boxed) in front of the crossmember to spread out the load.(have to look closely at the pic because it's all black) I also used a Morrison kit because they use larger diameter tubing, etc., but I'm running a 500 inch big block so some of this might be overkill for your application. I know how hard it is to not be "doing something" when you have the stuff but please get the bed you will use and mount it with the correct cross sills, etc to establish your rear end location. There's nothing worse than having to re-do because it just doesn't look right. Ask me how I know.