You will need to download 4.8, compile it separately and adjust the build process to use the 4.8 headers and libs.
I typically install a newer version and configure using --with-incompatible-bdb. Package "libdb5.3++-dev" or whatever's available.
It means my wallet.dat files won't work with clients that use 4.8, but I never use 4.8 and never share wallets, so I don't care.