Some good advice regarding both sides of the argument , really hard to make a call either way without seeing said van , and what are you wanting at the end of the day are planning on filling in windows and sunroof holes both relatively big job and how terminal is the rust, no point getting half into in and then deciding to pull the pin because you realise you have bitten off more than you can chew or found another van with less work. If your patient you will find another van and to the specifications you want ie:windowless good body etc sometimes we can all be impatient and jump in with out hearts and not listen to what our heads are telling us bus again without seeing pictures it really is hard to make a call. The first van I bought I didn't think was a sandman I just wanted a van it turned out to be a HJ Sandman body but the chassis had been replaced with a HQ at some stage, it also had a sunroof, a lot of rust not terminal but a lot of work had beautiful straight side panels I found my HZ Sandman before I had spend a cent on it and unload the HJ and got my money back, its your call in the end people get only give you their 2c worth.