Panel van conversion

[larscapaldi]

So I recently got myself an '83 van that had been standing in a yard for about 10 years. Think it used to be a panel van but was converted to a camper. A window had been cut out at the driver side but not done very well. I'm looking to install 4 windows now but not sure on how to do it. Is it possible to just cut out the size of the window from the panel and install one (I read somewhere you can get panel van conversion seals) or should I do some welding from the inside to make it a proper fit?

I added some photo's so you can see how the old window had been cut out, and where I am already with my project :p

Thanks in advance

Lars