Capital gain on sale of plot of land

Yes, you may claim exemption u/s 54F, and the indexation for the cost of acquisition shall be the year when the previous owner acquired it (2005).

i dont think i can becuz u have to buy a residential property not a plot

Section 54F :

If any long term property is sold then assessee can claim exemption u/s 54F, if he invest in RESIDENTIAL house property within 2 year if he purchase and 3 years if he constructs...

You cannot claim exemption under Sec 54F, because you invested in plot...