Typically the installation of an electric water pump conversion on the LT-1 includes a soft plug to fill the drive hole in the water pump, but does nothing to fill the hole in the front cover instead depending upon the original shaft and seal to close off the engine. This isn’t the best idea since the shaft is only supported at one end when its pump connection is removed. This can allow it to wobble and the seal will leak some oil and crankcase vapor.
If you pull the front cover off, you can remove the LT-1 timing set and replace it with any unit that is applicable to the factory roller cammed engines inclusive of the truck Vortec. Then just plug the old drive hole in the front cover with a soft plug. Check the cam gear for clearance of the thrust plate retention bolts, some of these will scrape on the backside of the gear. If this happens, either grind some material off the gear’s back side with a die grinder or Dremel Tool, or replace the hex bolts with Torx or Allen drive bolts.