Cutting LWB steel floor down to SWB

[RedRider]

Hi all, I've been browsing around here for some time now gearing up to chop down my 1970 C10 using the new Brothers template.

I plan to purchase new SWB sides and use the existing front and tailgate. I'm having a hard time swallowing the $1k for a new steel floor though. I'd like to cut it down but am having a hard time finding the specifics on doing so; apparently it's not as simple as 8" off one side and 12" off the other. Any help on this? I'd prefer to stay away from wood.

I'm getting really excited for this project, and I hope to share it soon!