Cap, I'm not clear on what happened to your motor. Was the conclusion that the 'bump" (must have been a hell of a bump:), caused the timing belt to jump cogs and thereby cause interference with the valves and pistons which trashed your valves? or did you suck water into the motor and that did it?
either way, it sux, but I'm in agreement with the rec to either get some new heads or rebuild, or did you mean by 'donor' you found another motor.

Seer

89LS,90LS,91LS,91LS,95SR,89JeepGrandWagoneer,90JGW,91JGW,92JGW,93RangeRoverLWB,93RRLWB,94RRLWB,94RRLWB,95RRSWB; 90'Dodgezilla' 1-Ton Cummins4x4.