Wngrog - here is your answer to teh different R-series trannys. Bascially the longer input trannys require a spacer....
The 1 1/8" steel spacers are required if you are using a 2wd Supra turbo R154 or a 3.4 V6 2wd R150, or 4wd R150F.
It is unfortunate that Toyota still uses the same R150 designation on the newer redesigned 3.4 trans that has an 1 1/8" longer input and matching longer release bearing.
This longer input gives more air space in the bellhousing resulting in greater cooling.
The 1 1/8" steel spacers are required if you plan on using the longer input transmission. The matching clutch release bearing must also be used.
