Here's a comparison, US to Finnish fuel prices. Prices off the net, the finnish prices converted to US dollars for comparison.
As fuel prices are high here abouts, fuel economy in daily drivers can be an interesting issue.

A "rolling" 1983 Chevrolet Caprice was purchased cheap, no engine nor transmission were included in the deal. The car's in pretty good shape, even if the color makes the eyes water. Here the 350 Corvette engine and TH-700R4 trans is going to be removed and returned to the previous owner.
It will receive the 305 cube engine and TH-350 tranny from the hearse, then be sold, just to raise some money for the main project car, the black one.

The Mercedes engine was hoisted out of a 1991 Mercedes-Benz 300 D.
Intake- and exhaust manifolds from a turbo version have been purchased and a turbo will be added.
Plans call for an automatic transmission out of a Mercedes Sprinter van.
The oilpan on the engine will have to be modified, and the propeller axle has to be built from a combination of Mercedes and Chevrolet parts.

There's precious little room in front of the tie rod, so the Mercedes oil pan has to be modified to fit the car.
Seen in this pic is the bottom part of the engine block of the Mercedes engine (front to the right).
Outlined in white is the oil pick up which will cause the oil pan to interfere with the steering.
The four cylinder version has a shorter oil pick up. Inset is a comparison between the six cylinder (top) and four cylinder (below) pick ups. The four cylinder version will be used as the oil pan can then (hopefully) be shortened enough that it won't interfere with the steering.

As we had a green Caprice with an empty engine bay in the garage, the Mercedes six was trial fitted into it.
The engine seems to fit surprisingly well into the Chevy.
The sway bar needs to be moved an inch or two downwards, and of course new engine mounts have to be made.
The diesel was hoisted out again and the 305/TH-350 combo mounted to make the car ready for sale.

A four speed automatic transmission out of a Mercedes Sprinter van was purchased from a wrecking yard.
This is the "large" version from a Sprinter 412 D or similar. It looks very high, so there may be some issues with the fit into the Caprice transmision tunnel.
(December 2013)

Today (December 13) the green Caprice was sold with engine and transmission from the hearse, so now we have some funding for the diesel project, and the garage is suitably emptied.

As this engine had a flywheel and clutch, they were removed, and instead the flexplate/starter ring was mounted on the crank shaft.

Engine and transmission mated for the first time.
All parts seem to fit perfectly, apart from the propeller axle (out of a Mercedes car), which has three mounting bolts for the transmission flange, while the flange has a four bolt pattern. A prop axle out of a Sprinter van would be the easiest solution to this problem.

As the Mercedes converter is prone to fall out of the bellhousing, a strap was made to keep it in place while working the transmission under the car, and up on the floor jack.

The Mercedes engine mounts are very bulky, so to avoid cutting into the cross member, Volvo engine mounts were purchased. Four of them to take the weight of the Mercedes diesel engine.

Hoisted into the engine bay and bolted to the transmission with a couple bolts, the general fit of the engine is evaluated, and the placement of the engine mounts is decided on.
The transmission fits just in the trans tunnel, and most likely will work without any cutting and welding. When it comes to a rear transmission mount, the original Chevy transmision cross member fits fairly well, and will just have to have a new adapter piece fabricated to fit the Mercedes automatic.

Here the four engine mounts are fitted into their new holes in the cross member.

The right hand side engine mount. Some tweaking and welding still to be done.
The problem for now is that to get to the engine mount bolts inside the cross memeber, the lower A-arms of the front suspension have to be removed. Might as well shorten the front springs a bit at the same time.

Two bolts hold the turbo to the exhaust manifold in this pic.The compressor needs to be turned about 180 degrees.
Everything looks like it will fit fairly well, the only thing needing major surgery being the oil pan.

Unfortunately the lower A-arms (or control arms, whish bones...) really had to be removed to get access to the new engine mount bolts. Even then it was not the easiest of tasks to get the nuts going on the threads.
As the springs were rolling around the shop floor they came into close contact with the grinder, and this resulted in these two coils being left on the floor after the rest of the suspension was back to a useful condition.
This should lower the front end some 1½", in this case depending much of the weight of the new engine and transmission combo.

The new engine mounts painted and ready to use.
(January 2014)

As the engine is bolted nicely to the car, it was time to fabricate a transmission mount.
The removable transmission cross memeber was used, but had to be moved a bit, so new mounting holes had to be drilled in the frame.
The new piece here, mounts to the trans case with three bolts, and lays on top of a Chevy transmission rubber mount, which in turn is bolted to the cross member.