B4 is my answer,its the most popular 2wd so there are loads of set ups for it and if you break somthing at a raceday the shop there should have the bits if not someone else will.
I've ran one for ages and they reward even the most cack habded drivers ( eyethankewe ).
I run a zx5 4wd because I wanted a shaft drive car that took stick packs, I havent driven a b44 yet but when I get a go on one ( hi rob
) my credit card may take a battering.
the zx5 is a good car but the b44 seems to be further advanced than it and as there are very few who run zx5's set ups arent as common sad realy as its a nice car to work on.