I agree with TSBB. Instead of trying to accommodate the boom roller...convert the whole thing to non rotating boom and rig it for slab reefing, that way you can also have a functioning vang, topping lift, or even a rigid vang, Just because it might have come that way 40 years ago doesn't mean it should stay. There's no resale value in restoring such a thing... it fact it would probably diminish resale, 'cause no one want's those old roller boom reefing systems.... they don't work.
My neighbors Columbia 26 pilot house had a roller furling boom... it sucked, I helped him fix it with a couple of self tapping screws to keep it from rotating.
A winch handle was needed to roll the boom. He had the old Merriman type winches, that use a flat bar handle. The fixture on the boom end looked similar to the top of the winch... the tang for the topping lift was part of a freewheeling cluster that allowed you to crank the boom with the TL attached.
All of this was so inconvenient... you couldn't but a cleat on the boom to control the topping lift... it had to be run like a halyard to the top of the mast then down to the deck.... he didn't even have it set up that way, because there weren't enough sheave's at the mast head... so it was just a fixed line...the previous owner would disconnect the TL when he was sailing. ALL of this bs just so you could roll the sail on the boom.... you couldn't really reef because there was no outhaul to pull the main's clew aft to keep the foot of the sail flat..... So the whole thing was just for storage... WTF????
Anyhow... we got together and figured a way to immobilize the boom's rotating, We mounted a proper vang and outhaul and rigged some slab reefing gear on the boom .... He was a very happy camper.