Old Leafsprung Land Rovers

Got a 2.5na diesel.

Used to do 70 easy then injector pump started playing up and developed a leak. Power dropped way down struggling to do 50.

Recon injector pump fitted as well as a new delphi lift pump. Engine runs nice on idle but kicks out black smoke on start up and has a haze of black smoke coming out the exhaust when driving. This has got worse ( did it only on dual carriageway but now its through town as well)

So im guessing injector issue? Only thing i havent changed in the fuel system or is it something else causing lack of power? Timing im pretty sure is good (or as good as it can be with the crude timing marks cast into the casing)