Torque Wrench Modify?

[Wrenchgear]

Hello there, new guy here....

I have an old torque wrench, (Snappy dealer called it ancient), QJR 3250, round head click type. He said "where did you get that?!? I told him I bought it brand new around 1984 or so, probably before he was born. Anyway, I need a repair kit for the ratchet head, and nobody can find one. I've been all over the web trying to locate one, but no luck. You never know, one could show up on e-bay next week, who knows?
My question is, does anyone know if an oval style head, from a newer torque wrench, possibly a QJR 3200 or something like that, might be interchangeable? Could I just pop out the rivet near the top of the handle, slide out the ratchet, get a new style head and re-install. Anyone ever do or try this?

Diagrams on these older ones are tough to come across on the web.

[macother]

I would advise against it. Proper torque measurements can be critical, and I wouldn't expect any of these older wrenches we have that are 80 or 90 years old, or even a newer one that's just 30 years old, to deliver accurately. Most industrial users replace or re-calibrate yearly, the ASTM's require it in many applications, and from a practical standpoint, knowing the difference between tight, tighter and too tight is a variable we can control only with tools working properly. I'd get a new one.