gauge cluster needs to be replaced...

Here is my problem. I bought a project bike wrecked with about 6k on the meter. The motor threw a rod not long after I got it road worthy 8 months ago. The motor I replaced it with has less than 4k and the bike has been restored from the ground up. The back side of the original meter is damaged and needs to be replaced but I dont want to buy a new cluster with high mileage even in good shape because I think it will take away from the ability to sell the bike someday(not that I want to sell it). Anew cluster is soooo expensive and it is hard to find one with low miles on the odometer. Can you replace just the back side of the unit or do you have to buy the whole thing? Can I pick up the whole cluster and use the white plastic back mounting tabs and keep my original display and memory? I dont intend to misslead a potential buyer but I think that if the guage reads lower more potential people will be interested if I decide to sell someday.