Re: two used roller furls - which one to buy?
..also adding a furler often interferes with an anchor on a bow roller (reduced clearance/space to launch and retrieve) so often a toggle or spacer needs to be added to make this workable.. also necessitating a shortened forestay. Mechanical end fittings can make this an easier thing to do, but in any case if the rigging is of indeterminate age replacing the forestay while you're at it is a pretty good idea.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)