W56 was only used in Toyota trucks. The 7M came paired with a W58, R154 (7M-GTE only) or an A134E; All use different bellhousings, clutches (if applicable), flywheels and driveshafts. You *should* be able to mount any transmission from the same series to a matching bellhousing but that doesn't mean that other changes won't need to be made; For example while a W56 will mount to the 7M-GE W58's bellhousing and clutch will work, the extension housing may need to be replaced and a different driveshaft fabricated.
With custom work you can fit a multitude of transmissions from various manufacturers in there; The Turbo Hydro 350 is one popular choice.
Yes, you can swap in a R154, but if you're car isn't making more than 350hp at the wheels I have no idea why you would want to... The R154 is considerably heavier and doesn't shift very smoothly compared to the W58. The gearing is almost identical (the big difference in gearing between GTE and N/A is in the differential).
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.
If you're so inclined I'm always more than happy to accept tips via PayPal. 
Tip Jar ---> 
|