Quarter panal help

[bigmac5300]

I am restoring a 1966 Ford Mustang, and the driver side 1/4 panal is is very ding up and the back lower part is rusted though,should i just pound out the dings and just replace the back lower part or replace the whole thing? and on the other side around the wheelwell is rusted out but the rest is good should i replace the whole thing or just around the wheelwell? and which is easier?

I also need to know if anyone can get me the frame measurement( the measurements from hole to holes on the frame) on a 1966 Ford Mustang?