cb360 intake manifold

my rubbers are cracked and leaking. i found these on ebay, please dont take them.
http://cgi.ebay.com/ebaymotors/HONDA-CB360-CB-360-INTAKE-MANIFOLDS-MANIFOLD-SET_W0QQcmdZViewItemQQ_trksidZp3286Q2em14Q2el1318QQhashZitem380045121873QQitemZ380045121873

you guys have any magic potions for saving/restoring/maintaining old rubber?

thank you