you can still order the 83 head new from mitsubishi. www.norcomitsubishi.com head MD060481 $948.00
Gasket kit MD997023.

I'm sure you don't want to spend that much but at least it is not some used junk. I have bought used 4d56 stuff. Most of it is worn out. Spun bearings, lack of clean oil bad heads etc. If you want I would sell you a Rebuilt head for a 84-85 model with the 18mm injectors complete with a nice cam for $750. i REBUILD THEM MYSELF. Thats ground valves, new stem seals, rebuild injectors. I check them for internal cracks etc.