Hi!
I've made two drawings for adapterplates to R154 gearboxes.
One to a friend which mated a Volvo B230 Turbo to a R154 transmission and put them into an Opel Ascona A.
He has been driving 540hp 630nm with slicks several dragraces without problems!
My project is a Reliant Scimitar with a Ford Mustang 5.0 H.O V8 and R154 transmission. I bought a Lakewood steel bellhousing intended for Ford toploader gearboxes. This bellhousing is shorter than the stock T5 bh, and that gave me the needed space for an adapterplate (19mm thick). And it will also protect my legs if the clutch explodes..
Here is a picture of the Toploader/R154 adapterplate drawing:
http://i124.photobucket.com/albums/p9/L ... rplate.jpg
As you can see the, boltpattern of the Supra gearbox isn't straight forward design...
We scanned the bellhousing on a big scanner, made the drawing with the scanned image as background. Measured all possible measurements with a digital caliper gauge (big one). Corrected the drawing and loaded it into a CNC mill.
A hint how to find the centre of the shaft is to look at the upper five holes in the round shape. They all have the same distance into the centre of the shaft..
Voila!

.oO Lucke Oo.