Do you know the honest fill capacity of the down in your bag? It may not be high enough to be worth the trouble.
The problem with V baffles is that you may not have enough room to reach in and get a fistfull of down.
I understand wanting to revive/modify a bag that is an old friend. I have an ancient Ski-Hut bag (as per Collin Fletcher) which probably had 650 cubic inch down when God was a little girl. I have thought about replacing the old down with good 800+ down, but the bag would still be on the heavy side because of the heavy-duty fabric. Consequently, it hangs in the closet while I make and use UL quilts.