early mk3's - ones with square side repeaters - can be fairly rusty, sills, wheel archs, boot lids etc. later ones with the oval side repaters had galvanised steel i believe so less rust worries.

as said, check electrics work. vr6's are the ones to get but i'm a bit biased! and mpg on the 2.8 i get about 19mpg, thats around town doing only short journeys driving like a looney. on a decent run mid to late twenties is easily achievable even when into three figures.