What is needed for a one-off manual trans adapter?

[LDO]

Is it simply accurate measurements and machining or is it an outrageously expensive nightmare? (Or something in between?). I want to build a model inspired by Ed Newton and Larry Wood sketches, a show/street rod that looks like a cross between a ‘27 Ford roadster and a Formula One car. Engine would be a Mercedes-Benz M119 V-8 and a suitable transaxle. There is no adapter for this engine, for any transmission or transaxle. 

Edited November 26, 2021 by LDO

[Ace-Garageguy]

In most cases, it's the former...simply accurate measurements and machining. 

I've built a few.

Often, the adapter itself can be machined from a simple flat plate of aluminum. A custom input-shaft bushing is made up to mate the gearbox nose to the crank end, the existing flywheel is drilled to accommodate a different clutch cover if required, and clutch-release geometry and linkage issues are resolved.

Sometimes, however, a complex bellhousing fabrication or custom casting is required, along with a specially made flywheel and associated components to mate parts from different vehicles.

It just depends on the particular application.

This one is somewhere between the two extremes: adaptor for a Yotota 2JZ to a BMW ZF/GETRAG 5/6 speed gearbox, using a flat-plate adaptor and a custom flywheel:

This adapter mates a 303-394 Olds to several GM manual gearboxes, and uses a custom, cast bellhousing (which a competent foundry could make for reasonable money if only one was required):

 

Edited November 26, 2021 by Ace-Garageguy
CLARITY and ACCURACY

[Ace-Garageguy]

ADDITIONAL INFO:

DeTomaso used a relatively simple adaptor to mate the Ford 351C to the big ZF 5-speed in the Pantera, from the factory, in a mid-engine configuration.

The Ford flywheel, starter, and pressure plate were retained, requiring only a clutch disc of the correct diameter, but with splines compatible with the ZF input shaft. A hydraulic clutch slave cylinder was employed to actuate an arm that slid the release bearing along a tube at the front of the gearbox...all very old-school, and reliable.

The RBT 6-speed version of the gearbox appears in the Revell kit below, and in reality, it's beefy enough to mount suspension pickup points and inboard brakes on the case...thus making a real-world setup like you want very plausible.

The ZF gearbox below is shown with the Pantera adaptor and side covers.

 

Edited November 26, 2021 by Ace-Garageguy

[LDO]

That’s all pretty wild. Want to make another one??? ? Or for a Ford 6R80 to put in my real 1987 190E. 

Edited November 26, 2021 by LDO

[Ace-Garageguy]

12 minutes ago, LDO said:

...Want to make another one??? ? Or for a Ford 6R80 to put in my real 1987 190E. 

Ya never know. Once I get the machine shop set up again out West, anything's possible.