This would be more work, but I would think about buying a new 3880, using its carts to test the two old ones you have, and then, assuming they work OK, sell them. You might get enough to break even.
An alternative is to buy a set of inks, test the printers you have, and if they don't work, sell the set of inks to reduce your loss.
BTW, when my 3800 developed head problems, I didn't want to risk spending several hundred dollars to get it world on with no guarantee that it would be OK, and I was able to sell it for $125 with full disclosure without ink.