If you are looking for more interior room/comfort and the vehicles are in good shape, it sounds like a good trade. The '85 will give you the opportunity to do things differently than with the first rebuild, and the Z will give you something cheap on gas to drive or sell to fund the Runner project.

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