well the bodies will cost around 500 area and upwards if your looking at bike bodies (i may be selling mine if your interested) and bike carbs depending where you go will cost similar price, about 350 to 550 area, i know shenpar do a bolt on bike carb kit, and bogg brothers are very good for bike carb kits too, but you will need standalone with bodies, and thats going to be 500 to 800 depending on if you go for predator or something like omex dta or emerald etc there will be other minor things like throttle cable filters just small bits that arnt a huge cost but will add up quick, but with carbs you will need 2 adjustable fpr,s the carbs, choke cable, longer throttle cable, and you can run on std ecu or run a dizzy, also depending which way you do it you wont have a rev limiter so will need an aftermarket limiter like the omex rev limiter which is 100quid i think
if you go onto rallye register theres a large number of people that run bike carbs and all rate them highly and seem to make good power too, they will be able to give alot of good advice on them if you go towards bike carbs. but yes its seen as going back a step, but it will be fun and you will still see good gains with it and in theory it will cost less too than throttle bodies, how much im not too sure but it should do anyway
i found one guys results on there earlier and he made 142bhp at the fly with 1.6 bottom end, s1 rallye head with ph4 cam and bike carbs which imo considering he hasnt had head work or anythink, just pocketed the pistons to suit the cam.
but its up to you mate, i think bodies will run more efficiant and are easier to set up and might see slightly better results, but for the cost of bike carbs and for what you get it is still a good option if your looking for something thats fun and runs well'ish lol