Depends on year and valve covers. My car is '69, and the tall valve covers hit the brake booster. But Branda has/had repros of the Cobra logo CJ covers.

The other problem is changing plugs, but not too bad with practice. The one under the master cylinder is the only really horrible one, and it could probably be easier done from underneath.

Headers are a special form of hell, though. If you install headers on an FE-block in a '67 to '70, I'd think real hard about a little blue Loctite on the bolts. Used to have to tighten mine every couple of months, and some of them are right against the reinforcement plates on the shock tower. The CJ manifolds are available as repops, and with the ramp-lock bolts, they seem to stay put and still breathe okay.

But the pickup will get headers. Let me know if you want some photos of the engine installed in the '69 car. It's tight, but works okay. Oh, and motor mount insulators seem to be getting a little harder to find. The local Napa dealer didn't have a clue, so I went to a Mustang specialty house.