Turbocharged 300, 5 speed and 3.55 rear gets my vote. Alot of your problem is the automatic and the high gear ratio. Automatic sucks alot of power and the 2.73 ratio just isn't low enough for the 300 to do it's thing at higher altitudes.

 

I've thought of swapping a manual in, but there's one big problem with that- It's hard to fit your feet in there when you wear 13 wide steel toe boots. The footwell is actually tighter than the one on my Courier.

 

Well crap, how about a built 300 with an AOD and lower rear gears? Those 2.73's are killing you.

 

i hate diesels and love i6's but the mercedes sounds really cool and functional for your application. i'd do it just for the uniqueness of the swap

 

Well, the van is getting worse and I can't take it off the road for very long right now so it looks like a warmed over 300. Most likely I'll have it bored .050 over, run 360 pistons and modify the intake to take a 2BBL sideways, with the dual EFI manifolds and a 2.5" exhaust.
It's tight under that doghouse, I don't know if an Offy intake would fit.

 

Why not get a painless wiring harness to put an injected 300 in there, you'd be more than happy with it.

 

If I were to go EFI, then I'd pretty much follow my current plan and add a 2BBL TBI setup run by Megasquirt.

 

TBI is crap, the same issue man, central point of fuel entry, leaning the outer cylinders, the fuel injected engines have injectors in the intake at each cylinder, the all get an equal amount, you aren't getting my point, the TBI is no better than runnin a carb!

 

The thing is, I don't want 40miles of wire and a computer controlled ignition system in this van, plus have you seen an EFI 4.9 in one of these? It's tighter than should be legal. It would also add complexity to the swap, while I can continue operation on a carb while I build a harness and then swap on a TBI unit in a day without disrupting too much.
I used to subscribe to the lean/rich theory, but now I'm not so sure. Having maintained a few of these engines over nearly 100,000 miles in trims from neglected stock to new and very hot, I haven't seen that much difference especially with a sideways mounted 2BBL. The center plugs might be a shade darker than the outer plugs, but I have never noticed a difference in wear or head/piston deposits between the cylinders. This goes from an engine that was idled for camper power without a thermostat until the bores were smooth (I've seen an engine with 250k that had less wear) to a 300-6 overbored to .060" with a 240 head and Offenhauser intake, DUI distributor, and a quite hot cam that could burn 35s on dry pavement through a C6 auto. The current engine in the van does not show any difference between the plugs, and it still is completely stock with a freshly rebuilt 1BBL carb.
If I had the desire to put a multiport EFI 4.9 in, then I would have listed that option.

 

i still say mercedes diesel. sounds right and should work good,get some mileage and make you happy. if you can let it sit for a bit you can do it and wouldnt you wanna do it right the first time rather than do it over again

 

If that Mercedes has over 300K on it be sure and throw in a timing chain, it's a good engine, but at 3 liters it's possibly slower then a fresh 300.

 

I really want to do the Mercedes diesel, but due to time I'll have to go with a 300. The Mercedes swap will take too long, I can't have the van down for more than a day or two while I swap out the engine. So, I'm going to put flat top pistons in a late 70s 300-6, a hotter cam, mild porting, and modify the stock intake to take a 2BBL and still fit under the doghouse.
I guess that for now I'll have to just finish up my Courier build and enjoy the diesel in it.
It's getting a new timing chain, oil pump chain, rear main seal, vacuum pump rebuilt, and a badly needed valve adjustment along with a few tweaks to the pump for now. I'm modifying a spare intake to have a better flowing elbow and connection for an intercooler, then I'm going to put on a modified VGT with mechanical control in the next year or so. Should be interesting being able to spool off idle.