I’m swapping to a steel front diff and I’ll be selling my old diff on eBay.  I was thinking I could either sell the housings and gears all separately, or all together ready to fix a blown up one, or I could do the weld mod to the diff which would allow someone who can’t weld to install into a manual hubs installation. 
What do you think would be the best for resale?

I think you'd be better off leaving it as is. Not everyone wants a locked or welded front. Your number of potential buyers would drop a LOT if you weld it.

I suspect your definition of a welded front diff is not the same as his - he has a second gen, so the front diff contains a pneumatic freewheel clutch, which can be problematic, and some folks weld it engaged and then fit freewheeling front hubs - the end result is a front axle assembly that is equivalent to the ones you have.

Yes I don’t mean a “Lincoln locker” I mean a disabled air actuation device via smaller welds.  Essentially it creates a typical open diff. 

Okay, & yes I thought 'lincoln locker' when I read the OP. I'd still say your market will be wider if left stock. You could always offer to do the mod to a potential buyer if they want it.