There are goods spots on either side of the bridge. Just upstream of the bridge which is basically the beginning of beat no. 1 is a great confluence, where there are some monsters fish and much to my surprise some monster turtles too !!!! Keep walking further upstream, cross the river when need and permissible (there are several spots as water volumes in Ramganga are not too high.
Downstream from the Marchula starts beat No. 2 and then three and thereafter 4. Beat No. 2 has some nice spots too, but more towards the end. Beat No. 3 is great too, but be prepared to do tons of walking if you want to hit that. I have never fished beat no. 4 as it is inside the park and is open to fishing only when the park opens. So it should be possible now ( i think the park is still open)
As for lures not working under the bridge, i think its a misconception because i have hooked a 6 pounder right under the bridge on a Jointed Firetiger. But i have seen the bait fishing that happens there, so maybe mine was an exception. I believe Mahaseer will eat almost anything it wants to, and considering atta lacks protein, i am sure they must be eating some river dwelling creatures to make for it, so don't give up hope of them not attacking a lure/spoon.
Basically if you have two days, definitely do beat no. 1 and then either 2 or 3.
Have a great trip and tight lines.