The new steering actuators from mercruiser (8M0063382) have quick disconnects on them. Can I just remove them and put my threaded lines onto the new actuator? Is there anything else different about them?

Your old steering hoses are SAE and the new quick release are metric. Mercruiser sells a kit with the new style lines, but its pricey. Maybe try calling a local hydraulic place and see if they have some kind of adaptor fittings you could use.

Just a follow-up. I removed the new quick-disconnects and was able to screw my lines in directly.

Just noticed your boat is a 1999 which has the newer style actuator, thought you had the older Saginaw steering actuator which uses sae fittings. Glad you were able to use your old hoses.