Even if the labels are the same, the construction of the tube can vary batch to batch. I think that it's essential to rebias the tubes when replaced, especially if the older tubes are vintage and very old. The old tubes could be US made, while the replacement are Russian or Chinese, totally different tubes.
It's not hard to rebias the tubes, but if it means working in an open chassis with high voltage you really need to know what you're doing.
You could try new ones, they sound thin from underbias, or might runaway from overbias and blow up and take just a fuse. But they could damage something more valuable.