If no money has been spent on the 8 3/4 already, it's a no-brainer. Dana 60.
Doing all the stuff to the 8 3/4 will put the cost within a spit of the Dana, and the Dana won't break.
If he mods the 8 3/4 now, and has to build a Dana next year, will he be happy? I think not. Better to spend a little more money once than a little less money twice!
R.