Yes its hard turning square stuff in a 3-jaw.

What size chuck are you looking for, think a C1 is limited to 80mm

I might still have a old 3" one that you'd have to make a backplate for, and find a chuck key to fit... its worn (its probably c1930) but usuable. If I still have it its your for £20 +P&P

Theres one here: BURNERD 4" 3 JAW LATHE CHUCK FITTED BOXFORD BACKPLATE | eBay

But a new one is only £50...