120mm reba's would be up to it, very sturdy fork, basically a shorter travel revleation, the revelations are llike lighter pikes, i wouldnt bother with u-turn and wouldnt go for 20mm axle if your budget is limited , some 140mm revelations would be perfect i reckon, reliability is good and they are very easy/quick for serviceing. The revelation can be adjusted internally to 120 and reba race upwards can be put to 120mm, very little weight difference between reba and revelation unless theyre u-turn, but will be probably 1 pound+ lighter than your z1 (3.8lb reba/rev)