So LS1. Lots of hard work, but it can be done. There are places that sell adapter harnesses etc eg Castle Auto Electrics in Victoria. The conversion is significantly harder than a Holden 5.7, but probably worth it in the end hp wise. If it was me I'd just buy a whole VR or VS (except late VSIII) engine and auto box and stroke it to 5.7L. Will bolt straight in using HQ-WB sump, pickup, engine mounts etc. Just needs a TH350 gearbox crossmember slightly modded and a shortened tailshaft. Electrics and fuel is relatively easy, but the time consuming part.