I'm guessing the 605 didn't have a starter on it when you got it. I would think the best right thing to do is to find a 605 gas starter.
At this point, if you really want to mount the diesel starter in there, you need to know if the bendix on it has the same number of teeth as the correct starter for that gas flywheel. If not you probably will have issues with it either binding up or shucking teeth off the ring gear.
does your clutch mount up? That was a big issue for me putting a 403 in a UTS-diesel.
Also, will there be enough clearance in the bell housing for the engine to bolt up with the starter mounted on it. (That was another issue when putting a 403 in a UTS-diesel.)