This conversion is really hard thats why not many people here have done it. Youd be better off starting with the AE73 chasis because then you can just bolt in your 4AG, you can even just plug in your engine loom straight up to the engine.
If you are not very good with engine stuff dont even bother trying to do the KE70 swap .. unless you want to take it to a shop to get done... most arent too bad at doing them and pretty cheap at $3500-4000