Well, check Mercedessource.com for decent parts and price. Should you ever want to put fresh injector tips in (need to be pop-tested and balanced if you do) get some Monark brand tips, just an FYI, there the shiznit as far as MB tips go, the cheapest, best and work great with Alt-fuels.
Far as turbos go. Since yours is an 85, they did kinda oddball stuff the last year before they went to the SDL with the 6 cyl.
Looks like the turbo in the picture is an AiReaserch. I say that because im running an 85 KKK brand K-26 on mine and it looks diifferant. The 85's have that pod on the compressor housing regardless of turbo brand. Thats the ARV (air recirculating valve) thes to bleed boost off for emissions. Since mine is been rid of emissions crap, I blocked the ARV valve off on mine by a super spring inside. course no vaccum line on it too. The 85's also had a fuel rack position sensor on the engine side of the injection pump. My spare/parts motor that i have is an 85. I robbed my K-26 off it :rofl:
Generaly speaking, the Garrett/AiReserch T3 is better performing for cruise/highway, it has better spool-up at speed and max efficancy around 12psi. Its a bit laggy'er since it has a looser housing. The slightly smaller K-26 is better around city driving, little tighter turbo and spool-up is better but dosnt pull as hard up top. Its max boost efficiancy is around 9psi. Remember these suckers are IDI diesels and run almost 22:1 compression so cant get real wild with boost. Ill have to look tomorrow to see what A/R these stockers are. They could benifit from a more modern computer designed turbo! I'd swap mine out if i didnt have so much goin on right now. The "Cats Meow" for these is a VVT turbo from a Jeep Liberty or Sprinter van, but gotta do some fabbing to fit one up and make the mechanical vane controls. Thats the route im gonna go. Do a bit of lookin round with the search button, ive posted up a bit of MB tips & tricks that might be of use to you! :hug:
Gimme a shout if theres anything you need, i'll do my best to help