switching tops and side?

[xarar]

I have been thinking about cutting holes into my case 840 from antec, and I recently saw this new case for 40 bucks shipped at newegg.com that has a hole and fan already cut into the top and side could I buy that can replace the top and in my current case?

They look to be the same dimensions but I cant find the dimensions of my 840.

heres the link

and heres the one for the dimensions link

thanks for any comments.