[HawgRyder]

A fair sized water pump of the gear variety and a valving system to provide some back pressure would give the engine something to push against if you are worried about RPM run away.
That is all an engine dyno is BTW.
I had a friend that built one...sent the engine to have it dynoed on an expensive unit...then mounted his engine on his own home built dyno...and used the engine to calibrate the valving and flow to give the correct curve.
Seemed to work quite good.
Bob