I may be wrong, but I don't think you can just add a second axle in front of the current one. I think you will have to move the current axle back when you add the second axle to maintain load stability.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed