True dimensional 2x8 insulation question

[Dean Klein]

Hey everybody! I've got a duplex built in 1888, and have a couple of cold rooms, upon inspecting the basement, there is no insulation under the floor of these rooms. The floor joists are true dimensional 2x8. I've been doing alot of research but still have questions. It looks like R-25 Batts would be ideal being 8" thick to fill the space however R-25 is not readily available from what I can tell. What is the recommended R-value to use? R19 being 5.5" won't fill the cavity, and the 9.25-10" that R30 comes in would mean that it would have to be compressed a bit. Any help would be greatly appreciated!