How bad is the leakIJ Can you tell where it is coming fromIJ Is it possible that the is an injector line cracked where it bols to the pumpIJ I replaced 1 line 3 weeks ago with the same symtoms. Hope this is some help
Pump sounds definite but injectors also. Have valves set while tuning her up. If it is cold enough it wouldn't surprise me for it to take awhile for her to hit on all six. Them old Allis's are a little testy at 40F and colder. Make sure thermostats are causing engine to get up to operating temp before they open. Get her tuned up and make sure she runs smooth when warmed up and you should be OK.
If you still have miss with it warmed up you best to quit using. The blast from compresion into oil from bad leak along side piston could foam the oil. Foamy oil can take out bearing!!!! It is rare to lose a valve and head has to come off reguardless so I'd just start there. Good luck