Would a dummy work for you? I may have a SW7 complete dummy loco.
One on ebay
https://www.ebay.com/itm/HO-scale-P...183941?hash=item48e2f26dc5:g:z7UAAOSw2oVehrSx
I found my dummy, Illinois Central, complete in original box. Trade for most anything Union Pacific, reefer, old time box car. Pictures in a few minutes.
View attachment 46179
View attachment 46180
In case you do not know, the SW7 early Blue Box version had a tiny motor, cast zinc flywheels. The second generation Blue Box had a longer motor brass flywheels.
I know the longer motor does not fit in the early frame. I have not checked the drive train for differences.