If you can afford 3/8" or 1/2", I'd go that route.
I looked up a steel weight calculator. 3/8 plate = 183lbs. 1/4 = 122lbs. 1/2" = 244lbs. I have to manhandle it by myself. No forks, lift or hoist unfortunately. I think 3/8 is the most I can do without risk to life, limb, and herniated disk.
Ian