hi just looking for some help,my second car is a vr commodore,i bought it because it was cheap. its been converted to gas,but the engine is pretty f**k,so looking to change engines,as i have a rebuilt spare,but the rebuilt engine is just standard...no engine mods for gas. so im wondering what parts need to be hardened or changed to run gas/petrol

Nothing.

Just make sure you have good coil pack, quality ignition leads, quality plugs gapped to 0.8mm and a new oxygen sensor and you'll be fine.

Regards,
Dave