Does anyone know if the bellhousing to trans body bolt pattern is the same for all w-series transmissions?

 

They're not necessarily interchangable. W40/50 transmission bellhousings (I'm assuming R series engines here) can't be swapped with bellhousings from W55/56/57/58/59. They're not as deep on the W40/50, because the shaft isn't as long.

The W55+ (W55-W59) should all be the same bolt pattern at the transmission, and same depth and bolt pattern at the engine (again, assuming R-series engine).

However, if you have a W55 and a W55 R-series bellhousing, you can put it on an R-series engine that originally had a W40/50 transmission, as long as you remove the W40/50 bellhousing.

The problem some people run into is getting a transmission that would work, but attached to a bellhousing intended for a different motor (I'm looking at you, W58, you whore of a transmission).