So if the E153 tranny and the s-54 have been mounted to the 3sgte, and we know they fit.

My question is, for both trannies, are there any physical differences between them as far as the passenger mount.

What i mean, is the clearance of the mount, engine and body on the passenger side are the same?

sorry for the vague question, but im trying to determine if i build a custom passenger mount for a custom engine, while i mount on the s54 and then change to the e-153 and that mount will still work?

um, neither transmission have anything to do with the passenger mount. use the mount for the engine going in the car. and if you are using a custom mount it will work with either.