Engine Conversion help!

I think that's a relatively easy swap. The major expense would be replacing the sump with the G Wagen version required to ensure clearance to the front diff. Alternatively you can get someone who can weld alloy to alter the car sump. I'm reasonably sure it will mate to the manual gearbox. 

To be honest if you are going to the trouble of an engine replacement I'd go for a 606. The 603 (as you will know) is a nice unit but at the end of the day it's only 113bhp.

A 606 turbo will need the electronically managed injection pump swapping for a mechanical one off a 603 unless you have the knowledge to separate the E Class integrated engine and gearbox electronics.

Tony, IMHO I suggest you speak directly to Gordon as he knows this stuff inside out and will give you unbiased advice.
Russ

  thats the way to go no electrics no heat problems plug and play

  with a bomb proof engine

the design of the G-Wagen was started as far back as 1972

https://en.wikipedia.org/wiki/Mercedes-Benz_G-Class#History

Britain's automotive tech wasn't great in the 1970's with the odd exception but the real issue with older cars is rust, something that no one got to grips with till the early 80's, Porsche excepted. Emissions and fuel consumption issues have driven much of the engine development too not always wisely, Fords lean burn technology to me was a better option than the catalyst. 

http://www.howacarworks.com/technology/lean-burn-engines

Mercedes and the other German car manufacturers used Bosch fuel injection systems in petrol cars that date back to the Messerschmitt BF109 in the 1930's right up till the mid 1990's, ultra reliable but super-ceded by electronic systems that may not be as reliable in the longer term but give more power and better fuel efficiency

The only generalisation you can make overall is that older vehicles were simpler but also less reliable

same 5 pot diesel that was used in the w460  

Long lived granted but in todays world, tooooooooooooooo sloooooooooooow  zzzzzzzzzzzzzzzzzzzzzzzzzzz

​Worse than caravans for holding up the traffic.

I guess this is a little tricky in that everyone has their favourites and I don't want to disrespect anyone's pride and joy.
My least favourite G is the normally aspirated 617, I'm not denying it's longevity and almost legendary status as an unbreakable engine but God it's slow and rough.

Next would be the turbo version. I've driven a few, one of which had been inter cooled and tweaked to allegedly 140bhp. I really didn't like the power delivery, really borrow torque / power band and still rough. The cabrio standard one I drove did feel quite sprightly but still suffered the typical turbo diesel on off norrow power delivery.

Next would be tie between the 280 petrol and the 603. Maybe ignoring the fuel economy I'd actually prefer the 280. IMHO a unnecessarily berated and underrated engine.

My 606 n.a. a relatively easy and uncomplicated swap, especially in to a 603 463. Maybe I'll turbo it but with a few tweaks I believe I've got around 150bhp of flexible and refined power.

Favourite is easy. The factory 606.

Great spot there Scouse G! Even though it was a bit noisy reading and lots of smoke, amazing what you can do with the 'black stuff'.

Spider1V

Label everything carefully before you take out the petrol, then you have to work out what you do and dont need as you go along, no easy answer I'm afraid.

Gordon Diesel Oilsgerby