[DCD]

Both the naturally aspirated RB25DE and RB20DE were used in R34 Skylines.
Here is a list:

4-Door Cars:

25GT-X Turbo (RB25DET)[MT & AT]
25GT Turbo (RB25DET)[MT & AT]
25GT-X (RB25DE)[AT only]
25GT (RB25DE)[AT only]
20GT (RB20DE)[MT & AT]
25GT-X Four (RB25DE)[AT only]
25Gt Four (RB25DE)[MT & AT]

2 Door Cars:

25GT Turbo (RB25DET)[MT & AT]
25GT (RB25DE-LEV)[MT & AT]
20GT (RB20DE)[MT & AT]
25GT Four (RB25DE)[MT & AT]

I dont think the chassis number will change depending on engine. The engine code should be typed in the chassis plate

Hope this helps.