I rethreaded my BJ8's bellhousing last time I had it out; previously, I'd made do with some 'make-a-thread' goop that worked well enough (those bolts aren't particularly stressed). IIRC, I used 'ThreadSert,' not 'HeliCoil' brand, which are equivalent. 3/8" 'fine'--24tpi if I'm not mistaken--bolts are used all over on Big Healeys, so it pays to have a kit handy (in particular, they're used for the front shock mounts, which are easy enough to strip). I use red (strongest) threadlocker on inserts, and I've never had one come out. Unfortunately, I don't think it's possible to drill and tap for inserts in situ.