Here is the deal. In most cases individual throttle body intake manifolds are not long enough to give you any ram effect at low rpm, so they are almost strictly race pieces and usually very expensive also.
You could get an old quad webber intake for a 289 and get some webber replacement throttle bodies and weld in injector bungs, but it will be really expensive, it won't make any more power than a good box intake and it will have to be speed density unless you duct all of the air through one MAF which kind of defeats the purpose.