dependswhat size and how many webers u use.
I recently bought two twin 40 mm side drafts for $300, but thats a good price, they in good nick too.Then u need a manifold - about $170 - $200 there. Call errol at
www.datrats.com.au -
hes a good bloke and will give u the best price.
Unless you going to modify the engine , you can get them tuned real lean, but theres not much point in that. Mods that are useful are a different cam, head porting, exhaust( as the webers
put a lot through an engine, it needs to breathe clearly)and maybe fuel pump upgrade, but stockie would probably do.
You may be able to use an a14 or a15 head - they about $150 - $250 i guess.
Hope this helps....
Linc.