I've come to this thread late. Anyway back in 2008 Scott at Monarch lathes posted a bit on Practical Machinist about their remanufacturing of 10EE's. He included a list of chucks they could provide. All were steel bodied Pratt Burnerds: four jaw chucks, 6 inch and 8 inch; three jaw chucks, both 6 inch and 8 inch. An 8 inch 3 jaw seems big to me but its use on a 10EE is not unheard of. When I bought my (used) 10EE it came with an 8 inch 4 jaw Cushman. I thought I'd never have a use for a chuck that big but of course I soon found the extra size was quite useful. Most of the time I use an easier to lift 6 inch 4 jaw Buck.
David