hi m8,
well lots of things to mention about the 3,
make sure ya get one with a good body on it... front sills around jacking point like to go,
smoking when driving, ussually piston rings etc...
stalling/hunting - usually simple as split vac pipe - but can be maf meter or sensor,
bad fuel economy - needs a good service

cant think what else without boring ya, lol.
then its your choice on engine, as said, have a search on here, its been covered loads and there is bags of useful info to aid ya get a good n

hth
ps - when i say look at mine, i mean show ya the above problems lol
