You can run a little more boost on the RB20 with the RB25 turbo as the engine is smaller in size with supporting mods and 14psi 200rwkw is probably possible but im not sure how long the turbo would last at that boost level.
I managed a 13.6@105 with a crap 2.4 second 60 footer on a 30 degree day, with my R33 first time at drags. So in your case with similar power less weight better tyres and suspention high 12's may not be out of the question.