Using water to remove water buildup is a age old back yard trick and lots of have done it successfully and lots have not.
Essentially the water turns to steam and steam cleans the inside of your block but the caveat to all this is that you pour too much water and you could end up hydro-locking...
Dieseling can be a cause of many things but the most common is build of carbon that remains still ignited causing the vehicle to run longer than needs to.
Have you crawled under the truck and did proper adjustments to the linkage for the shifter? This is 90% of the time why you can't get them to lock in place for.
Your throwing money at the truck for no good reason. Stock HEI systems working perfectly out for the majority of builds out there.
People insist on putting aftermarket coils, and big plug wires and blah blah and wonder why things don't work.
Get a OEM distributor with a good coil...