if you get a used rb make sure you pull the sump off and take a look, make sure the is no sludge or shavings, also check the welsh plugs they have a habbit of rusting through, if you go down the rebuild path it will cost more but make sure you go through a workshop that will warrent their engines, the only workshop that i have seen do this first hand is Trojan Morotsports, bit more expensive but worth it, the problem with rebuilds is that it always that if i only spend a bit more i can get this and this, set a figure and stick by it.