Fuel pump is on the carb side of the head, between #2&3. Set engine at tdc to unload the lever on the cam to ease removal. there's a phenolic spacer which needs a gasket on both sides, between spacer and head and spacer and pump. A torn lever boot will let oil leak out thru the pump lower housing. Mitsu starions have a block off plate for the head hole, and then you can go to an electric pump and a pressure regulator. You need the flow dumped by the regulator to feed the Mikuni carb accel pump and the normal supply to the fuel bowl.

I'd car wash the engine, let it dry, and then run it hard for a short time, then dust the motor with baby powder to find the oil leak path.

Old mitsus need the radiator rodded out, or you'll need a new head gasket soon. Trust me on this one.

Check the shifter for fore-aft flop as you get on and off the gas. Excessive flop means you need to rebuild the tranny pretty soon. Neither hard nor expensive to do.

You WILL need to replace the idler arm bushing, and maybe tie rod ends on the steering. Try to buy just the idler bushing kit instead of the whole arm assy.

That should handle the obvious gotcha's.

Note that head oil leaks are most often (1) valve cover gasket. (2) fuel pump. (3) rear cam plug. (4) distributor housing oring. (5) front half circle cam plug.

Valve cover can be warped by overtightening. Check for flatness.

One other sneaky leak is from the point at the back of the head where the upper and lower rear cam bearing halves mate. On engine assembly, you have to smear rtv on that metal to metal joint to get an oil seal. Possible to fix with engine in car.

Turbo that baby for one fine little sleeper...