Putting NH 499 head on a Heston windrower

This is my first year with my Heston 6610. I went from a pull type mower to this older self propelled because of my small odds field shapes. The head on the 6610 is my least favorite part it is 16 foot and single sickle. I would like to put on a 499 head because 12 foot would.be a better width for me also I believe the 499 will be able to cut faster to make up for smaller head. I should just be able to hook hydraulic drive right to new header right? How bad of idea is this?

Putting NH 499 head on a Heston windrower